After a lot of playtesting and vassal and brainstorming and the like, I figured I'd do a quick rundown on how I feel about each unit, and where my lists are at personally right now.
Necron were my very first 40k army since returning to the game from a brief bit of playing in High School. So, I had a bunch of Necron models lying around, and we've gotten a fair # of games in here and there, plus via Vassal.
HQAnrakyr the Traveler - This is my favorite HQ. He's cost appropriate for what he does, works just fine in a Command Barge, and his "vehicle control" is actually reliable (in a way that something like Chanegling never was). Movement talented players will find using Overlords w/ Scythes in Command Barges pretty simple, and they're pretty darned useful to have around. Anrakyr is the best of these, though you don't want to do any other special character in a barge.
Most important thing to consider when weighing him vs. other Overlords is Anrakyr in a Barge =
1 unit of Immortals gets SLIGHTLY better; this actually can be semi-useful in a larger unit w/ a warscythe lord attached for your "advance" troops ... they aren't going to fight anything especially dangerous any better than regular Necrons, in that they are going to die horribly, but S5 attacks and a warscythe will allow them to punch most basic marine type units in the face pretty good (Esp. led off by tesla carbines). Don't underestimate this in a list built with it a little bit in mind.
An Overlord w/ Warscythe, Barge, Tachyon Arrow is 210 points
Anrakyr w/ Warscythe, Barge, Tachyone Arrow, Control Vehicles, Buffed Immortals is 245 points
Can you find 35 points in many lists to give you the power to control things like Psyfleman dreads at least once in a game, and to slightly (ever so slightly) improve one of your Immortal squads? Um, yeah.
Imotekh - There are a lot of internet know-it-alls out there posting in as contrarian and loud a fashion possible about how awful Imotekh is ... chillax please. His lightning bolts are plenty relevant and useful for a long-range-meh army, night fight is valuable and replaces one Cryptek's worth of points (55) plus a 2nd overlord to enable a 2nd Cryptek, and of course this means you can keep that "Turn 5 backfield objective protection" solar pulse for Turn 5 either way. He's not over costed because of this, though he only works in certain lists. You lose a Scythe Command Barge by having him, but you do gain Phaeron. His lightning bolts are absolutely worth a single Eldritch Lance, and his night fight is stronger than a single Solar Pulse in lists that aren't long-range-shooting intensive at all. Take out 55 for the Eldritch Cryptek w/ Pulse he replaces, and take out the Phaeron you'd buy in a list with a Phaeron'ed unit, and you're looking at a 150 point Overlord with 2+/3++. It's fine. Just don't put him in lists simply because ... put him in lists he belongs in.
Most of the other lords and such - Trazyn has some value, and his value will increase when 6th rolls around and Deathmarks become better (scoring Deathmarks that doubletap on the move, thanks). The rest of these special characters kinda suck, as far as I'm concerned. Nemesor's abilities are fun but I don't think you'll see a lot of good use out of him ... he doesn't have the same pros as Imotekh, but still costs more than an overlord would, and doesn't have a warscythe ... so you lose the value of command barge flybys.
Speaking of which,
Command Barges - These suckers are your win-machines. Hidden power fists, meltaguns, psycannons, sanguinary priests, Coteaz, and a million other things are perpetually at a 50/50 chance of being allocate one-shot without a save when a fast AV13 skimmer 24"'s over their heads. Scarabs will roll over 10-man marine squads with a fist ... if you flyby gank the fist first. You'll be able to dakka down FNP BA ... if you cut down the Priest. Two command barges gives you 6 swings, to boot. We already know they gank tanks just fine with their +2d6 rear armor hits, but the key to these units is their ability to single out giant pains in the ass for Necron ... hidden pfists, sanguinary priests, coteaz, etc.
There are obviously plenty of times where you aren't going to be able to just run your Barge over enemies ... they aren't going to let you, or you won't be able to without sacrificing your lord inherently to the return fire, etc. It is often a good idea to give the Lord a Tach arrow, to have one of the lords be Anrakyr, and to enjoy having just a couple more Tesla shots on a durable platform. This sucker is a great unit ... and its mechanics amplify with player skill in a very gratifying way.
Crypteks - These guys are good for Eldritch Lances on backfield scoring warrior units, and for Solar Pulses. If you want to get creative and do other things with them, be my guest, but that should be reserved for the player types that really don't need my input. 2 Crypteks means you can solar pulse away your opponent's alpha strike ... and also means you can do it twice in a pinch, or protect your backfield scorers from lategame firepower to clear them from objectives ... probably the most overlooked advantage by the average player. They also of course couple with 3+ cover and small sizes to protect Scarabs from a desperate alphastrike by opponents who really don't want their psyback spamming, dreadspamming lists to get disintegrated by them.
Lords - There's nothing wrong with a warscythe lord in a unit or two, especially if you wind up with a furious counter-attacking immortal unit ... which suddenly gives you a power fist that doesn't go at I1, and helps ensure your wussy immortals can actually win a midfield combat against a marine-heavy force on rare occasions ... this can actually come in handy if you are facing something like blood angel jumper spam w/ a few priests, b/c these types of armies can get up in your face, murder whatever vehicles you have with melta, and FNP through your teslatorrent ... whereupon you have warscythe barges to target some priests, a lord with a scythe in an immortal unit to suicide target via base-2-base another priest, etc. etc. You won't use these nearly as often as a few Crypteks of course.
This section of the FOC is the one upon which the largest dumperoonie was taken. It is not strong.
Triarch Stalker - This sucker is ... well, not very good. Open topped AV13 with a 2 shot 24" missile launcher. Yes, it's AP1, I know ... but it's not a two-shot multi-melta in the way it would be for an army like marines, and it's on a vehicle. In order for it to be anything more than a very expensive double-missile dreadnaught, you need to be within 12" of your target ... which means you're readily target-able by return melta fire from a huge array of armies out there, and your own vehicle is extremely fragile.
It is additionally expensive enough and unique enough in the dex that any kind of opposing ranged anti-tank fire is going to be leveled at these guys ASAP, should their firepower actually be threatening in the first place. They're too expensive, they don't shoot very hard, and they twin-link an army's worth of equally lame long-range traditional anti-tank fire ... whoop dee doo. Don't try to build a max-long-range-shooting army with Necron, or you will end up disappointed in Necron.
Praetorians - 1 attack, I2 and no invul on assault jump infantry? Blah. These are crap.
Lychguard - It would make so much sense if they shuffled some things about between this selection and the one prior. Give Lychguard jump packs, and enable them to hitch a ride on a command barge in squads of 5 ... or swap weaponry and gear around so Lychguard are simply jump-capable, and Praetorians have a longer range AP2 shooting attack that's a power weapon, as a counter-assault-capable unit that can actually fire while trudging along the board.
The problems with both of these units are related to the really awful dedicated transports Necron have ... but I'll hit that up when I cover Dedicated Transports.
Deathmarks - I suspect these will be amazing in 6th edition. For now they are crap.
Flayed One - Call me crazy, but for cheap I can actually see taking a squad or two of these and outflanking them to attack long fangs and/or tie down gundreads and other sorts of shenanigans. They really aren't all that expensive for 15 S4 attacks on the charge, even though they are really easy to kill, and Ld10 + RP will occasionally help you stick around for a combat or two that you lose by a model or two. These are "bad" in the same way Mandrakes are bad, and good in the same ways ... and as such there's actually occasionally reason to take them, especially since there's nothing else in the barren wasteland of Necron Elites. If for some reason you feel like having a few affordable models in your list that can outflank into someone's backfield ... go ahead. I haven't been finding myself with spare points to include a squad in most of my list builds, so please don't translate this to me saying Flayed Ones are good. I just think people will put them to good use if they have 5-10 of them in a handful of list archetypes.
C'tan Shard - 3 Psyfledreads statistically kill 1 with a round of fire. Lots of people have 3 psyfledreads. You can only put the ranged anti-tank weapon on one of them, for an absurd points cost. They still use really tall impossible-to-easily-hide models. They cost a crapton. They are WAY less durable as a result of T7. No, it won't matter as much for the weapons that need 6's to wound T7 or T8, and I'm not talking about lasguns. I'm talking about multilasers, psycannons, psybolt razorbacks, missile launchers, autocannons, psybolt autocannons, lascannons, plasmaguns, plasma cannons, plasma rifles, meltaguns, grenade launchers, hell WHATEVER .... every attack in the game S6-S9 just got better against C'tan, and that's a huge quantity of the current metagame's firepower and combat power. AND if you want them to e very good at all, they really didn't drop in price all that much. When I heard you could take 3 C'tan I was excited, b/c I love monstrous creatures. When their points and stats came out I was very disappointed. Fortunately, the Heavy Support section would save me later on.
Warriors - These guys are cheaper, but they are dramatically weaker. They still are effectively very short-ranged, and their firepower is not all that effective (Even with gauss) unless they are in large #'s and attached to a Phaeron. I'm not saying you can't do this, but I think they're kind of an underwhelming unit in all respects if you want them to be offensive at all. The best use for Warriors right now = filling out your Troops in points-restrictive builds with 65 point scoring units that you can hide in backfield and/or attach lances to. Most opponents won't be able to take focus off Scarabs and Spyders to kill them, and if you think they will just reserve those units.
Immortals - Unfortunately there's no strong ranged anti-tank in Troop for Necron, and this applies to Immortals as well, but Tesla Carbines are extremely good anti-infantry firepower, and the Assault nature of the weapons is a very important component to keeping your Immortals out of combat longer w/out losing firepower in the process. This also obviously combines with the assault nature of Eldritch Lances when you take a few to up your "hope I get lucky and hurt a tank" firepower.
Personally I've been enjoying taking 2 larger Immortal sqauds and 4 minimum warrior squads for scoring, though sometimes it's more 4 immortals / 2 warriors ... all very list dependent.
Night Scythes - So Night Scythes are how you get Tesla Destructors when you use your Heavies on "NOT Annihilation Barges." Night Scythes are also how you contest objectives and periodically try to transport small squads to objectives. Night Scythes are just plain AWFUL as dedicated transports. Fragile, easy to see (They will indubitably be on the large valk flyer bases), hard to cover, and with 24" range firepower ... they're everything bad about Twin-Assault Cannon Razorbacks, but even worse in that they knock their occupants back to reserve when they are killed, are less likely to have cover while also being able to fire, etc. They also of course cost 100 points, which is pretty damned pricey for such a fragile platform. You're paying for some really weird crap here ... like 12" to move and shoot all with a vehicle that only has 1 weapon, the ability to move 36" (but no better cover save for it), and a fancy transport option that they really didn't think through. Even giving the option to "emergency disembark" with a dangerous test or something when it's killed would have been a perfectly fine fix, i.e. as the aircraft is going down the Necrons leap through the portal .... but the way it is now makes it not wise to ever use it to carry things unless you desperately need to race after an objective or something. Still, they have twin-linked Telsa Destructors, and twin-linked Tesla Destructors rock (Will talk about with Barges).
Ghost Ark - Look, I know some people are all about these, but ... a 115 point slow-moving melta-fragile open-topped transport with NO meaningful firepower whatsoever and whose occupants at best are going to have a single S8 shot at absurd points investment (at least 215 net points for 5 warriors + lance cryptek + Ark) ... is TERRIBLE. YES, they create this durable scoring unit ... but you're just as durable walking on from reserve with 5 dudes and hiding behind a wall or something near an objective, and walking over to it late with help from your 2nd Solar Pulse to keep from getting shot off. It's not like if a blood angel army full of meltaguns or something is in your lines ... you're going to somehow be just fine hiding in your ark. There are some rumors that point to being able to score ONLY from within OPEN TOPPED TRANSPORTS in 6e ... and look, that's cool, but Necron aren't wanting to score from inside their transports right now anyway, because their transports are pretty bad, and way too expensive. Pass. Deal with being afoot, and having lots of high pressure units to advance at someone, and having good suppressive and anti-infantry firepower, and learning to keep units not in transports alive. Not that hard. Bandaiding bad playing/moving skills with 115 point quasi-durable transports = not wise.
This is the money slot in the dex, IMO
Canoptek Wraiths - Wound allocatable, affordable units with solid WS/BS, S6 shooting attacks, lots of S6 rending attacks, multi-wound, jump back moving, terrain ignoring badasses. Many, many lists are completely justified taking a unit of 6, or a unit of 6 with particle casters, and letting them do their thing. They also make a legitimate "mini" deathstar in that they are FEARLESS, which is huge. Unless they FAQ entropic strikes to the end of the phase or end of combat swings or end of initiative step, they are also an excellent support unit for multi-charging scarabs in a pinch ... it's one thing to throw a bunch of scarab bases at vehicles with S3 against "I hope I reduce each vehicle enough" ... but it's another thing to have a bunch of equally multi-chargeable S6 multi-attack bases coupled in with that roll on reduced armor in case you whiff your entropic rolls on a few of your targets.
HERE'S an important tangent point. The Necron army has a ton of good anti-infantry firepower ... enough to punch a hole in most bubblewrap with relative ease. It also has units in Scarabs and Wraiths that are very fast moving and also very good at racing forward, multi-charging and instantly ganking or disabling large #'s of vehicles all at once. The traditional sound logic that "close combat to kill vehicles" is bad DOES NOT apply to Necron. You can do it on Turns 1 and 2, you can do it from a long distance away, and you can do it without sacrificing any of your anti-infantry firepower, large #'s of points, or scoring units. This is so dramatically different from every other codices' "close combat anti-tank" that you need to consider it, play around with it, and give it a shot.
Canoptek Scarabs - Akin to the above point, Scarabs are the heavy lifting anti-armor of the codex. Tachyon Arrows and Lances and Wraiths and Spyders in a pinch may let you deal with things like Land Raiders, but Scarabs are what let you deal with vehicle-spam armies quite readily. They are also amazing vs. dreads. They are also quite durable and fine against marine units that aren't force weapon or power fist enabled (and as above mentioned, Command Barges can pretty reliably help you deal with the power fist issue). One of the things to note here is that they will as often crush the odds as fail them vs. marines, b/c of the sheer # of dice and attacks you roll ... 10 scarabs charging 9 marines who just lost their powerfist (even grey hunters) are going to throw 50 attacks, 25 hits, and about 8 wounds ... and 9 counter-attacking grey hunters will throw 15 attacks for 10 hits and 6.67 wounds ... and you're going to get the charge on them reliably. This is a combat the Scarabs will invariably win, but they are just as capable of throwing 10 or 12 or 15 wounds w/ that charge ... and if they t hrow 0 you really don't care, b/c you lose 2-3 bases at most after res and the rest are done. These guys are tank maulers ... and they are MULTI-CHARGE kings due to their charge range and base size ... it's not unusual for a movement master to pull off multis against 3-4 rhino hulls despite an opponent spreading them some, and to kill or disable all 3-4 on one charge with a healthy 8-14-model Scarab unit (depending on Spyder spawns). It's also not hard to bang holes in even durable bubble wrap when you have a 12" charge to take advantage of whatever holes are made.
Tomb Blades - I never find room for these in my lists due to Scarabs/Wraiths, but they are plenty fine units for their points and firepower. Sad kinda. Crammed Fast Attack.
Destroyers and Heavy Destroyers - Similar to Tomb Blades in terms of rationale for not taking. Unfortunately Necron are too expensive to try and make a traditional "shooty" list with ... 3 x 3 Heavy Destroyers and 3 Triarch Stalkers = 990 points, and your firepower is pretty crappy and fragile at that ... 630 for 3 stalkers and 3 solo heavy d's ... still bad. Stop trying to build Necron this way, you will be disappointed.
Necron are much more like what Nids would be if Raveners were 15 points with a 3+ cover save, and had entropic strike, and you could take like 10 in a squad. Everybody would take a shitton of Raveners, and screw "all you have is Hive Guard" when you can chuck that many tank-murdering wounds across the board lickety-split. You also would not bother trying to shoehorn in crappy overpriced super fragile ranged-anti-tank Harpies ... or crappy overpriced ranged anti-tank Tyrannofexes. Starting to feel me?
I like the HS slots here ... lots of the units are interesting or worth taking
Canoptek Spyder - Killa Kanz, but cheaper and way more durable and easier to give cover to and better in combat and not one-shottable and wound allocatable and able to create 15 point scarab bases and can't burn out (Even though they can take wounds) and quite capable of running over several of the things that scare Necron combat wise. Plus they are great places to hide valuable characters you don't want to run away or go anywhere.
Spyders are the absolute badasses of the dex. They are slow as crap, they won't fight anything until late game, but so what? 6-9 spyders will break the back of most opponents and what they have left in a close game, and they'll power up your scarab swarms to stupid levels early game. Anyone who has played the 26 vehicle ork list, shot the crap out of it for 4 turns, laughed at someone trudging across the board with it, and then confusedly wondered what happened to their army at the bottom of turn 6 while staring at a couple of banged up Kanz wandering around in their backfield ... well, Spyders are going to do the same sort of thing for Necron armies that you shoot up and laugh at for 4 turns, only to suddenly have yourself broken in half with a bunch of wounded Spyders wandering around in your backfield. These are "win-loss tournament" Necron armies' wet dream. They are, in the same vein, terrible in battle point / massacre tournaments, b/c very often they'll only really help seal a close game, ensure a win, etc., vs. race forward and clear a board or shoot someone away. If you are one of the handful of very inaccurate internet players who believe 40k is simply a shooting game ... well, I can understand why you wouldn't like Spyders. I can also understand when you blame your tournament losses on bad dice, or when you base your opinion upon winning at your store all the time or having a "mostly good" tourney win-loss record, etc. This isn't meant to be inciteful of angry retort from said player type ... just insightful about Spyders. They are great.
Annihilation Barges - If you have slots not used on Spyders, or an army build that doesn't at all work with Spyders, these puppies are cheap, durable, and hit really really really hard. Pick up a few dice, and start rolling twin-linked tesla destructors against ... oh ... Rhino chassis, and Venom chassis, and the like. I need say no more.
Doomsday Ark - Awful. Unreliable, inaccurate large blasts on platforms that can't move to fire them and are probably also going to be low enough to the ground that crap's going to persistently be in the way, forcing you to move and reducing you to a S7 attack that's worse than a twin-tesla-destructor. Apply warscythes and scarabs to land raiders, torrent to terminators, and don't take one of these expensive crappy things.
Monolith - I'm sadface about the Monolith. It used to have the Doomsday Ark's large blast, but better ... Ordnance that can be fired on the move and is S9 AP1 under the hole (which, if you're shooting vehicles, was always all that mattered ... you either missed and were S4 so who cares, or you hit and the hole was over the target, so it was AP1). The gauss on it was nerfed badly, the main gun was nerfed badly (no more ordnance, no more S9, no more AP1 even under hole, etc.), the teleportation capabilities were nerfed badly, the durability was nerfed horribly ... should I continue? This went from great to crap. You could still take a trio of them and hope you run into someone so "meta" they go without melta ... or something ... in their Imperial army, I guess ... but even other Necron armies are going to laugh you off the board with things like ... scarabs ... and stuff.
Doom Scythe - The best anti-whatever gun in the game, bar none ... on a flying razorback that sits where cover isn't really possible, and doesn't have something machine spirit like to enable firing while maintaining a cover save ... and that costs a LOT of points. These are cool, but putting them to good use is going to be more a matter of hoping your opponent is stupid or fails dice rolls against it ... than a matter of you being able to skillfully apply it. I wish you could pay even a significant quantity of points to turn the Triarch Stalker's Heat Ray into a Death Ray. C'est la vie.
Such is my unit review. Here's the most recent list I playtested with ...
Anrakyr the Traveler - 165
Catacomb Command Barge - 80
Overlord w/ Warscythe, Sempiternal Weave (2+) - 115
Catacomb Command Barge - 80
Royal Court - Cryptek w/ Lance, Solar Pulse; Cryptek w/ Lance; Lord w/ Warscythe, Mindshackle - 150
Royal Court - Cryptek w/ Lance, Solar Pulse; Cryptek w/ Lance
10 Immortals w/ Tesla Carbines, Pyrrhian Eternals - 170
10 Immortals w/ Tesla Carbines - 170
5 Warriors - 65
5 Warriors - 65
5 Warriors - 65
5 Warriors 65
(Lord attaches to Pyrrians for QuartersVP, "most" advanced unit - still not crazy about CC)
(Crypteks attach to 10 Immortals for late-game pulse holder, and 3 warrior units, with 1 warrior unit typically in reserve for backfield scoring / staying safe)
10 Scarabs - 150
10 Scarabs - 150
10 Scarabs - 150
Annihilation Barge - 90
Annihilation Barge - 90
Annihilation Barge - 90
Just my $.02 as ever ... I'm no smarter or savvier than most of the other decent gamers out there, but I hope it's been helpful to some, or conversationally provocative to others!