Any co-op (2 player - 4 player) suggestions?

orcs must die 2,inversion,resident evil 5,sniper elite nazi zombie & v2

Sniper Elite V2, Sniper Elite Nazi Zombie Army, Dead Island Riptide, Ghost Recon Future Soldier also have co-op I think :)

sanctum 1-2, L4D 1-2, Orc must die 1-2,Magicka, Castle crashers,Nation Red uhm.. thats what i can think of atm.

Creepy? Dead Space 3, Alien Swarm, God Mode (more arcade and humorous, though), System Shock 2 definitely (if you feel like playing an old school game).

Dead space 3 (needs origin),
Far Cry 3,
Alien Colonial Marines (people seem to hate it, but Ok for me),
Inversion,
Sniper Elite: Nazi Zombie Army,
The Darkness II,
Saints Row: The Third (not creepy but loads of fun),
Kane & Lynch 2: Dog Days,
PAYDAY: The Heist (not creepy),
L4D1 and L4D2

Sniper Elite: Nazi Zombie Army was what came to mind.

L4D 1/2 - Custom maps... It's so Fun!
http://www.l4dmaps.com/
Some notice about L4D 3, maybe ?

Haven't seen any GTA IV suggestions...

The Incredible Adventures of Van Helsing

Probably unrelated but I don't think you can finish Killing Floor. It's a multiplayer only game with no story and with thousands of custom maps / tens of mods.

why not trine the original?

Dunno about any horror ones, but I saw a couple of suggestions I was going to make;

Orcs Must Die 2

Sanctum 1-2

Guns of Icarus Online

Forge

Left 4 dead 2

if youre looking for something preaty fun you should get trials evo gold. the multiplayer is kind of empty of people but its a whole lot of fun. and if youre looking for a shooting game far cry 3 is the right choice

LEFT 4 DEAD 3 THE BEST ZOMBIE MULTIPLAYER, 10.000 HOURS PLAY

Call of Duty World At War Zombie Mode.. played it many hours in coop, still very funny and imo much better than the current CoD Zombie Mode shit

MONACO

Wait for State of Decay, if people buys it it will get coop later.

try Cry Of Fear (yeah, it's finally on steam!) if you like horrors

There was a 'Stalker' F2P co-op game that got greenlight on steam, can't remember it's name.

Hammerwatch (Currently in beta, greenlight on steam tones of fun)

Just Cause 2 (with MP patch, fun as hell)

Magicka (be ready to rage at one another for friendly kill/heal boss to full health with orbs.)

Dont forget borderlands 2

Sven co-op - allows Half Life and custom maps to be playable on coop
System Shock 2

Dungeonland, castle crashers, god mode

God mode is really fun,not really horrorish but still