A friend of mine wanted to play a 5 tervigon tyranid list vs my gk army so I took standard all comers list that I'm working on for some upcoming tournaments. I have had really good success with it so far against some various armies.

Tyranids (not sure all of the upgrades, just what he had for bugs)
HQ
Tervigon
Tervigon
Elites
2x Venomthrope
2x Zoanthrope
2x Zoanthrope
Troops
10x gaunts
10x gaunts
15x gaunts
Tervigon
Tervigon
Tervigon
Heavy Support
Mawloc
Mawloc

My Grey Knights
HQ
Grand Master
-rad nades, blind nades, master-craft psycannon, 3x servo-skull
Elites
Vindicare Assassin
7x Paladins
-2x master-craft psycannon, banner, daemonhammer, 2x halberd, master-craft halberd
Troops
10x GKSS
-2x psycannon, psybolt ammo, daemonhammer, Rhino transport
10x GKSS
-2x psycannon, psybolt ammo, daemonhammer, Rhino transport
Heavy Support
Dreadnaught
-2x twin-link autocannon, psybolt ammo
Nemesis Dreadknight
-greatsword, heavy incinerator, personal teleporter

Mission: Kill points
Deployment: Pitched battle

I get 1 special rule to hand out and I select to give re-roll failed to wounds on 1s to my paladins. My main goal is to try to keep him isolated so he can't spread out and really use his numbers to his advantage.

Turn 1
GK: I advance my paladins, dreadnaught, both rhinos 6 inches, nem dreadknight 12 inches, vindicare stays where I set him. Dreadknight uses heavy incinerator to kill 4 of 10 gaunts on one of his flanks. Dreadnaught kills a sqaud of 2 zoanthropes. Paladins and grandmaster let lose 12 psycannon and 10 storm bolter shots killing 11 of the 15 squad of gaunts, 2 psycannons from inside rhino kill 2 more from the same squad leaving just 2 left in that one stormbolter from rhino does nothing. Vindicare takes a shot at a venomthrope that makes its 5++ save. 2 psycannons from inside other rhino takes shots at the venomthropes along with stormbolter from their rhino doing nothing.

Nidz: He advances his gaunts up to make room for birthing, remaining squad of zoanthropes advances along with venomthropes. Mawlocs burrow. Tervigon 1 spawns 15 gaunts with rolls of 4,5,6. Tervigon 2 spawns 14 gaunts with rolls of 4,5,5. Tervigon 3 spawns 11 gaunts with rolls of 2,3,6. Tervigon 4 spawns 13 gaunts with rolls of 2,5,6. Tervigon 5 spawns 9 gaunts with rolls of 1,2,6. So out of the 5 he had only 1 cannot birth anymore but that's still 62 more gaunts for me to have to cut through. His shooting is ineffectual and 1 of the 2 zoanthropes, thanks to dreadnaught, casts the s5 ap3 template at my paladins but they make their saves.

GK: 1 - Nidz: 0

Turn 2
GK: Dreadknight advances up 12 more inches and burns the remaining 6 gaunts from the squad he previously shot at. Dreadnaught pushes up 6 more inches and falls in behind the paladins and kills the other squad of zoanthropes with his s8 autocannons. Paladins push up along with a rhino that unloads its 10 gks from inside and their combined fire kills a squad of 15 freshly spawned gaunts, stormbolter from rhino kills 1 gaunt from another squad. Vindicare fires at a tervigon...and misses completely with BS 8, awesome. Other rhino moves up and takes some shots at the same tervigon with the psycannons from inside doing 2 wounds.

Nidz: Mawlocs show up both trying to arrive on my power armor guys that were now outside of their rhino, both scattering way off. Wall of gaunts pushes forward with the 2 venomthropes and the tervigons start birthing more. I lose track of how many spawn as they are starting to just blanket the quarter of the table I've begun to isolate him to, but 1 more tervigon cannot birth anymore luckily, bringing it up to 2 of the 5 becoming sterilized. Gaunt shooting does a wound to one of my paladin terminators, and a squad of 2 suicides on my paladins in assault. Other side of the table, my vindicare assassin dies horribly to roughly 25-30 gaunts shooting at him, starting to lose containment on one flank. The wounded tervigon unluckily suffers from perils of the warp trying to hand out feel no pain.

GK: 4 - Nidz: 1

Turn 3
GK: Dreadnaught side steps and kills the group of 2 venomthropes with the s8 autocannons. Dreadknight moves 12 inches towards the tervigons and burns up 4 gaunts from a squad of 13. Rhino moves out of the strike squad way and they fall back to deal with the mawloc ready to assault it but shooting takes care of it miraculously. Paladins and grand master multicharge a large squad of gaunts and the other mawloc cleaning up shop and consolidating closer to the tervigons. Rhino on far flank tank shocks 12 inches through the wall of gaunts up to the 2 tervigons up on that flank hoping that they blow it up killing some gaunts for me that are surrounding it like an ocean and leaving me some room for the squad inside to do some damage.

Nidz: He's feeling a bit demoralized at this point as I've only lost a vindicare and taken a wound on a paladin but he mans up and pushes onward. He births more gaunts with the 3 fertile tervigons after a slight repositioning of the gaunt wall, and he pulls the gaunts from the flank with the tank shocking rhino towards the paladins to try to take them out with volume of shots but has to wait till the next turn. He unloads more shots on the paladins now with help from the tervigons doing nothing, and shoots at the dreadknight with a squad doing nothing and then assaults the dreadknight doing 2 wounds to it thanks to poisoned attacks and I kill 3 in return with the greatsword it has. He does not assault the paladin squad. He assaults the rhino with 2 tervigons and luckily blows it up, if it wrecked I would have lost all 10 guys inside as they couldn't have piled out, scary gamble that paid off, lost a rank and file gk in the explosion and he lost a mass of gaunts from 4 different squads in the blast.

GK: 8 - Nidz: 2

Turn 4

GK: Dreadknight kills 3 more gaunts he does no wounds and fails his 3 fearless saves leaving it free to move again. The GKSS embark back on their transport since they had now dealt with the mawloc, and the rhino moved 12 inches to reinforce the far flank where my 9 grey knights were now alone and looking screwed. The dreadnaught takes some shots at a tervigon doing a single wound. The paladins and grand master charge 3 units of gaunts whiping them all out but unluckily they take 2 wounds in the process, one on an already wounded guy with a sword and he dies. My unit of 9 gkss multi-charges the 2 tervigons that tag teamed their transport in a ditch effort to cause mayhem, they do no wounds on initiative 4 with 8 guys that attacked so no attempt at the 3d6 shadows of the warp force weapon activation, initiative one my justicar with his daemonhammer kills the tervigon that had 3 wounds on it from previous turns lighting up masses of gaunts in wounds wiping a squad off the table, they kill 2 guys with psycannons and 2 guys with swords, I make leadership to stay.

Nidz: More birthing but now only 1 can still reproduce after its all said and done, lots of shots for no effect, he sends in a unit of gaunts to try to help the tervigon, killing all of the remaining men except the justicar who strikes on 1 with the tervigon and he magically pulls off the 3d6 force weapon activation with a roll of 7 killing the tervigon and another some gaunts in collateral damage but he dies from the tervigon attacks.

GK: 13 - Nidz: 3

Turn 5
GK: Dreadnaught throws out some shots at a tervigon doing nothing. Paladins kill another tervigon, the last one that could birth, and a squad of gaunts. No gaunts were in range to take wounds. Dreadknight shunts 30 inches and burns a couple gaunts, and the healthy squad of grey knights lay down shots into a tervigon doing 2 wounds.

Nidz: No more birthing was done, he multi-charges my dreadknight my 10 man GKSS with a squad of gaunts, and sends his last 2 tervigons at the strike squad. With the remaining 2 tervigons and a squad of gaunts that still drops 15 wounds on the unit and kills the dreadknight, my dice decide I would only lose my 2 psycannons to the gaunt attacks. My attacks end up 3 wounds to the tervigons but I tempt fate and try for force weapon activation and my justicar explodes out of the squad, the tervigons roll like wet noodles and only kill 1 of my guys, I make my check to stay.

GK: 15 - Nidz: 4

Roll and game goes to turn 6.

Turn 6
GK: Paladins arrive and multi-charge like champs finishing off the 2 tervigons and the gaunts because that's what a banner allows to happen.

Nidz: No units left.

GK: 18 - Nidz: 4

It was a crazy game, I honestly thought it would be a closer game with all the hordes piling in, I believe he could have done better if he played more aggressively to my weaker flank. Overall the casualties were
Nidz - 160+ gaunts, 2 Mawlocs, 5 Tervigons, 4 Zoanthropes, 2 Venomthropes
GK - Vindicare, Rhino, 10 GKSS, 1 Paladin, Dreadknight, 4 GKSS

My MVP was the dreadnaught that killed the 3 units that were going to cause the most damage to my army in 3 turns.

His MVP was the collective birthing of the tervigons.