Tyranid Armies Raptor has Tested

Currently, I've tested one real army type, and that's bringing Hive Guard with Tyrannofexes for a solid gun line, and packed Tervigons in for psychic support and troops.

Tyranid Big Guns, Model 1
Tyranid Prime
3x2 Hive Guard
2x10 Termagant
2 Tervigons, Catalyst, Adrenal Glands, Toxin Sacks
2x18 Gargoyles, Toxin sacks & adrenal glands
6x Shrikes, Lash whip/bone swords & scything talons
2x Tyrannofex, Cluster Spines & Rupture Cannon

Tyranid Big Guns, Model 2
Tyranid Prime
3x3 Hive Guard
2x10 Termagant
2 Tervigons, Catalyst, Adrenal Glands, Toxin Sacks
3x3 Spore Mines
3x Tyrannofex, Cluster Spines & Rupture Cannon

Basic Thoughts on the Components & the Whole
This kind of firepower is adept at taking out vehicles. Hive Guard allow you to hunt light mech, while Tyrannofexes can hunt light mech and threaten heavier armor. Don't RELY on them to KO the heavier stuff, but they might be able to slow a Land Raider (I mean, you're happy if you just immobilize the thing).

You will be using the Tervigons as point-defense; you'll basically be launching waves of beefed-up Termagants at anyone that wants to assault you, and the monstrous creatures CAN be thrown into assault. Timing's an issue, since you don't want the Tyrannofexes in assault longer than ncessary. That said, T-fexes and Tervigons both have four S6 power weapon attacks, though the Tervis are poison, so you're generally looking at a 4+ with a re-roll to carve something. (...unless it's, I dunno, a Wraithlord? Then it's just a 4+)

Against infantry, you have Cluster Spines, and in a pinch the Tyrannofex thorax swarm. S5 AP5 is reasonable; it'll wound most things handily, if they don't have better than a 5+, well...

The Tervigons and Termagants
The obvious con? Kill points. Against something like a double-raider army, expect to lose at least two units to screening your assets and absorbing the assault. If the enemy gets close, you shoot the crap out of them, then make sure your Tervigons are close enough to buff the termagants.

On the bright side, the Tervigons can score, and you should be able to solve your troops worries, unless your dice are bad. On average, you'll get about 20-22 termagants out of each Tervigon, and you'll get that over two turns. 3d6 should see doubles after a couple turns or so, and rejoice if you get more. Cry if you see three 1's the first time you drop the dice.

Cons with the Build
The latter build lacks speed and mobility. You'll have to plan ahead to take the objectives downfield, since there's the issue of your slow speed. I like that build one has some speed to it; the Gargs and Shrikes are a mobile reserve AND good for cleaning folks off objectives in a pinch. The gargs function as added punch, and a flying cover save.

Frankly, if you're going to range far ahead, you either need shrikes/warriors to detach and advance, or you need to make sure you can get Dominion off reliably, and trail some gargoyles back. However, if you get out of synapse, bear in mind that gargoyles have something like Ld6 and can't survive losing a combat.

The Mobile Element
Think of Gargoyles as a crossbreed between Hormagaunts and termagants that can't score. You have speed, a gun, and are reasonable on the charge; on average 20 gargyles will hit about 20 times; you'll auto-wound 2-3 times and you'll probably rack up another 8-10 wounds, roughly, after that. Not BAD, but you're still T3 and have an amazing 6+ save.

Shrikes...well, I think I'd prefer poison; it costs a little extra but it lets you tag monstrous creatures and makes you nastier against the smaller gribbles; S4 that wounds about 75% of the time against T3-4 is not bad at all, AND can handle larger gribblies. The downside is the 5+ save, so you HAVE to bring 5-6 or so, and it's an expensive unit. Use cover, don't fear the terrain checks, and trust the lash whip to even things out for you when you have to go into terrain.

The Prime
I've grown to like the prime. On the one hand, a Hive Tyrant is much nastier in combat, and can bring a heap of support abilities/psychic powers to the table. On the other hand, a tyrant with guard and a gun is close to 300 points. A Prime with the minimal whip/sword is 95 points, and can hide in a unit. He's a few extra anti-S8-hits in a Warrior unit, or a little extra durability for a Hive Guard unit, and it's hard to ferret out THAT synapse.

In the Future...
I'll be testing out triple trygons, and eventually harpies. Zoanthropes are on the to-build list for April, as well (albeit scratch build, but I'm not buying 9 of THOSE too. Hive guard are cool and will see lots of use. Not necessarily the same for Zoanthropes).

Also, I intend to test Hormagaunts as the core as well, perhaps with some Warrior support. We'll see.