WaaghSteve:
Just for my two cents:
I have also found that Tyranids tend to run either as Nidzilla (a lot of MCs) or Horde (lots of Guants).
What is distressing for many people is that Carnifexes (the backbone of Nidzilla lists), can be made into assault or shooty monstrosities, and it can be daunting to deal with them. But in the end, remember that Shooty Carnifexes rarely have more than a few attacks (think of them like a big Dreadnaught), and thus can be brought low with PK.
Also, they can be either 3+ or 2+ save MCs, so it is important to figure out which ones you have a prayer of hurting with shooting (2+ MCs are much more durable).
Hive Tyrants (the other MC flavor) are also fairly tough, but are S6 creatures, so in the end, they're killing normal boys pretty well, but you don't have to worry about them instant killing your Nobs.
The Tyranid Codex is rather interesting in that there are a LOT of upgrades available to the many broods, and it is difficult to tell what each group has been upgraded with. Just be aware of a few nasty ones (I usually mentally note these for early destruction):
1. Feeder Tendrils
These must go. Absolutely. They provide the unit (and units near them within a small radius) the USR of Preferred Enemy. Yes, even the MCs.
2. Warp Field
People may not tell you, but it is a pretty nasty 2+/6+ upgrade, so be careful.
3. Leaping
Leaping nids will usually hit you first. With fleet, they have an effective 24" charge range (if they roll well), so it's often going to hurt.
The Tyranids have a few other nasty abilities but they are mostly of things to note:
The Horror, which forces a Ld Check before you assault them (not good for Nobz squads w/o an IC), and as always, flesh hooks (which give them assault grenades).
That's all that comes to mind immediately.
But really, play to your opponent rather than his list.
Look for weaknesses, especially in deployment.
Tyranids rarely have an easy time with Mech (kind of like Orks surprisingly), and can be outmaneuvered. The smaller guants can get in the way of things (and cover objectives), but they're not much better than guardsmen in assault. The Big MCs are scary and huge, but really, you have PK. Herding smaller Nids by Tank Shocking is also fun, as they don't really have much that can hurt vehicles (just don't try to Tank Shock an MC). Apply Skorcha as necessary once they are clumped up.
Oh, and a word on synapse: A number of creatures generate this controlling field, but once they are taken out, the smaller guants will have to make some pretty hefty checks to act normally. Otherwise they will mill around. Most decent players will overlay Synapse fields, but it's always a comforting sight to watch that big horde of guants that were about to hit your lines mill about sniffing the scenery.
Best,
-BT
