I've been playing Tyranids properly for about six months now, and have had mixed results sio far in. Anyone who knows me will understand that I am certainly NOT a competitive player (indeed, I had to ask someone what WAAC stood for recently), so my lists are more a mix of 'what have I got that's fully painted?' and 'what's fluffy?'. Now this means that whilst I am not necessarily picking the best army list, I do have to try that bit harder with my tactics in order to beat my usual Marine opponents!
Whilst I'm pretty au fait with the Tyranid Codex by now, I'm still not convinced that there are that many ultra-powerful builds from the book, although I dare say the tinterweb could offer all sorts of cookie-cutter lists - but that's not really my style. My usual 1,750pt list now consists of:
HQ - Tervigon with Catalyst & Onslaught, Scything Talons & Adrenal Glands
EL - 2 x Zoanthropes
EL - 2 x Zoanthropes with Mycetic Spore
EL - Doom of Malan'Tai with Mycetic Spore
TR - 10 x Termagants
TR - Tervigon with CVatalyst, Scything Talons & Adrenal Glands
TR - 17 x Genestealers
TR - 18 x Genestealers
FA - 3 x Spore Mines
FA - 4 x Raveners with Deathspitters
HVY - Trygon Prime
The plan with this army is relatively simple, and plays to the Tyranids strengths whilst trying to minimise the Codex's much-discussed weaknesses.
The one thing Tyranids do exceptionally well is offering a near limitless number of bugs. Whilst on their own Termagants are weak, in quantities of a hundred or so they do two things: one, soak up valuable missile launcher and bolter rounds, and two, scare the living daylights out of most opponents! That is, in fact, what the Tyranid army is all about for me - an unending swarm of bugs to hold and contest objectives, backed up by a few stronger units to knock out transports and opposing threats.
This is where the Genestealers and Zoanthropes come in - both unit types offer essential anti-tank capability, albeit in very different ways. The Zoanthropes are a very obvious unit to play - put 'em in midfield and shoot (and hide your more fragile units before the invulnerable saving brain-bugs, to boot).
The Genestealers, meanwhile, are my second anti-transport unit. Whilst most folks would suggest infiltrating them, this is actually tantamount to suicide with these glass hammers, Whilst deploying 18" from your opponent is great, you are almost certain to suffer one, if not two shooting rounds before you can charge your opponents' transports, by which time your Genestealers will be little more than purple gore. My preferred way of using Genestealers, then, is actually to play a little more cautiously - something that most Tyranid players struggle with. Most folks see the army as a pure close-assault army, and therefore rush it forward at the earliest opportunity. Simply speaking, THIS DOES NOT WORK! What you'll do is spoon-feed easy to kill units to your opponent, who will simply sit back and shoot you to death, whilst occasionally feeding you a cheap unit to slow your advance. What the Tyranids really need is a degree of patience. Of course you need to swarm forward, but you need to advance in cohesion, using your bigger creatures (in my case the HQ Tervigon, Raveners and Trygon Prime) as a screen to provide the Genestealers with a much-needed 4+ cover save. This approach will mean your Monstrous Creatures take a pounding and die relatively quickly, but you must console yourself that this is their job! It's not the big creatures that will win you the game, it's the objective-holding troops - the Termagants. These easy-to-underestimate bugs are your secret weapon. Whilst your opponent is shooting the big threats (Zoanthropes and MC's) your game-winning Termagants will be hoding in cover and keeping their heads down.
The biggest weakness in the Tyranid Codex is the criminal lack of anti-tank shooting. Now before you tell me (quite correctly) that the Zoanthropes and Hive Guard are the best anti-tank shooting units in 40k, you just can't have enough of them! And once you factor in psychic tests, poor range and the fact that these creatures will be your opponent's number one target early in the game, you just can't depend on them.
In fact, games involving Tyranids can be simplified to three simple cases:
1. If your opponent is a foot-army, the Tyranids will win.
2. If the Tyranid player gets first turn and gets extremely lucky with his anti-transport shooting, the Tyranid player might manage a lucky win.
3. If the opponent stays in his tanks, he will win.
Unfortunately (for me anyway), it is as simple as that! Paper, scissors, stone. I'd love to hear from other Tyranid players for your thoughts on how to play this army effectively!