Co-op game recommendations anyone?

Killing FLoor

havent read the other comments...
Bulletstorm (has a fun coop and a good single player),
Magic: Duell of the Planeswalkers 2012 (if you like card games),
Payday (brilliant game),
E.Y.E. Divine Cybermancy (a bit complex and hard to understand sometimes but full coop campaign),
Kane and Lynch (1+2),
Left 4 Dead (i prefer 2),
Nation Red,
Lord of the Rings - War in the North,
Portal 2 (pure 2 player fun),
and of course killing floor,although I really recommend to play this with 6 players.

I do not recommend: Bunch of Heroes(boring) and Magicka (fun in the beginning but pretty fast gets boring as you will probably always spam the same spells); Dungeon Defenders itself is a brilliant game but there are too many DLCs. If you are fine not being the badass high end pro gramer that owns nightmare mode it's a good game

Edit: HOW could I forget Borderlands,Borderlands is awesome

Saints Row 3

Definitely Saints Row the Third, Borderlands, and Portal 2. If you're into MMOs, I used to play free one called FlyFF (Fly For Fun), which was a port from Korea...fly at level 20! The game is quite fun, although most of the economy is controlled by the "Cash Shop" and it's a total grindfest at higher levels.

This site is great

Magicka / Dungeon Defenders / Upcoming-Torchlight 2 / Renegade Ops

Kane & Lynch,
Gears of War,
Borderlands,
Trine 2,
Dungeon Defenders,

DotA2 only :)

Splitscreen/Hotseat-Games are the best in my opinion :D
Trine, Lara Croft and the Guardian of Light, and..
Clonk Rage. I know, it looks ugly like hell, but it is really funny at some point.

Try Resident Evil 5. It seems perfect for you two.

wait for Orcs Must Die 2

dead island.it on sale now

Call of Juarez: The Cartel. Crappy game, but really well suited for co-op. You work together killing criminals and against each other on secret goals. Tough to explain, but great co-op. It was expensive on Steam last time I checked but I bought it in stores for under $10, and I've seen it on sale (Steam redeemable) elsewhere.

shoot many robots was ok, for 10 dollars its worth it but they need to add more content into it

F.3.A.R

Saints Row: The third! But right now , get Dead Island.

You can get a bit more out of left 4 dead 2 with map mods. But i'd also have to second Guild wars 2 if you want an MMO.

Magicka, dungeon defenders

Borderlands

HL2 series w/ syngery

Rayman Origins (sadly quite expensive) and A Virus Named TOM have local co-op

Killing floor ?

High recommendations for Magicka, Trine 2 (and Trine, assuming you can do the local co-op), Sanctum, Serious Sam 3, and Torchlight II (not quite out yet, though).

Obviously it depends which genres you like :)

Other considerations: Beat Hazard (need Ultra DLC), Lara Croft: Guardian of Light, Magic: The Gathering (can 2v2 against bots, or play archenemy with bots), Might & Magic: Clash of Heroes (can play 2v2, though the 1v1 is fun to play, I rarely like to play 1v1 with friends but enjoy it a lot), Spiral Knights (free), The Darkness II (personally don't have it, but my friends enjoy it).

Get Half-Life 2 and Synergy (a co-op mod available directly from Steam). Trust me on this.

L4D1/2 , PayDay, Sanctum, ya... and Resident Evil: Operation Raccoon City should be cool, but i dont have it :/