"The Tyranid codex is an exercise in masochism" - can't remember who, can't remember the discussion thread, but it sums up the metagaming feel nicely.
This seems to be the feeling I get from many, many people on this forum. I actually feel that the Tyranids are better described as an obscenely high-skill army, that doesn't play remotely like an MEQ force, and thus causes a lot of people to fall flat on their tactical behind. While some units in the codex are pure tripe (I'm looking at you, Pyrovore, you overpriced lump of fail), what has struck me the more I read and re-read the codex is the absolute need for army units to complement each other. Where an MEQ force can usually spam effective units (and now I'm looking at you, Long Fangs and Razorbacks), the Tyranids seem to actively punish most spam style lists, because every unit you take seems to require another unit to work at maximum effectiveness. They especially require careful manipulation of enemy threat perception; tricking your opponent into attacking seemingly high-priority targets while moving the real killers into position.
My thought was for those of us so inclined to post examples of units from the Tyranid Codex, discussing how they support other units. I was going to begin with the obvious ones we've all worked out, and then hope that people can suggest new and useful ones (anyone who manages to find a single decent synergy for the Pyrovore wins the thread).
So...
1.) Heavy Venom Cannon + Carnifex.
Unit with Heavy Venom Cannon hits high armour target. Cannon "stuns" vehicle (due to -1 on damage roll). Carnifex charges immobilsed vehicle, eats it (strength 9 +2D6 laughs at AV14.)
This strategy also works with Heavy Venom Cannon + Ymgarl Genestealers (due to their placement rules) vs light tanks (as enough Rending attacks means AV 10/11 will eventually fall to Genestealer claws).
2.) Venomthrope + Horde (unit of 20+ weenies: Termagants, Hormagaunts, etc...)
Venomthrope stands inside Horde (which "circles the caravans", so to speak), provides 5+ cover save. Weenies provide 4+ cover save to Venomthrope. In assault, Venothrope moves to the front to use lashwhips to reduce enemy attacks.
Flavour with High Priority Target (Hive Tyrant, etc...) to force enemy to leave the relatively "useless" Venomthrope alone in favour of avoiding insane number of attacks from weenies/hideously damaging attacks from High Priority Target.
Flavour with a 10 model unit of Deathspitter Tyranid Warriors + Prime to really force an opponent's hand; there's not a whole lot of infantry units that can withstand 30 BS 4, strength 5 shots, followed by a 30 model Hormagaunt assault...
3.) Lictor + Trygon + Deathspitter Raveners
Lictor appears on board (out of LoS, but very close to enemies - preferably ones not too good in assault) when available, goes to ground for 2+ cover save. Trygon and Raveners appear without scattering, shoot the place to pieces; next turn, assault begins. Trygon goes after high-priority targets (tanks, characters, etc...), Raveners deal with everything else. Lictor hops about, either being Teleport Homer, or else attacking weaker targets of opportunity, then using Hit and Run to leave combat.
Right, what else is there?