Looking for good online/co-op games

Killing Floor

Trine 2, Sanctum (and probably Sanctum 2, haven't played it yet), Orcs Must Die 2, and Lara Croft and the Guardian of Light are all games I've had a lot of fun cooping.

Spiral Knights isn't by any standards great but is fun. Terraria is excellent

Portal 2, Rainbow Six Vegas 2, Men of War Assault Squad, Mount & Blade, Alien Swarm

FEAR 3. Great co-op shooter, but a bad horror game.

Thanks guys ^^ and if theres more .. let me know here :3

Shank 1's co-op was very fun.

Payday: The Heist

Payday

• KF
• BORDERLANDS 2
• Aliens Colonial Marines (horrible SP but if you have friends, MP and co op is way better)
• Sniper Elite Nazi Zombie Army
• L4D2
• Resident Evil 5/6/ Revelations (only good for action and co op)
• Payday The Heist

Oh, and Orcs Must Die 2

There is a site for just that:
http://www.co-optimus.com/system.php?id=4&sort=rating&direction=ASC

As for my personal recommendation - go for Hon (harder, but better) or Dota 2. With 5 mates and a bit of practise, it is really really good and the fun is endless.

Terraria = epic,
Left 4 dead 1\2,
Killing floor,
Dungeon Defenders,
Portal 2,
Payday: the heist,
Castle crashers (short but a lot of laugh),
Minecraft (forget graphics and you'll get a lot of fun)

Alien Swarm is a good choice of cooperative game in my opinion. It's based on the Source SDK, so graphics are decent at least. It should easily run on most computers, and it's free too. Recommended if you want an arcade style shooter :)

Killing Floor, Orcs Must Die 2

L4D2, Portal 2, and Payday the Heist.

portal 2, borderlands 1 & 2, guild wars 2, l4d2, alien swarm, terraria

Killing Flooooooor, possibly the longest lasting appeal as you get persistent leveling and perk grinding that actually feels rewarding.

Diablo 2

Resident evil 6 offers awesome coop experience , as well as Resident evil revelations

, splinter cell conviction was also much fun in coop mode

and if you haven't played portal 2 coop try it , it is very interesting

Garry's Mod, i played it with my friends using Hamachi long time ago, really liked it, building things together..etc

I was playing the Far Cry Assault co-op mod today. Really fun, also synergy and svens co-op.

I had a lot of fun playing Dead Island, Transformers: War for Cybertron, and Sacred 2 online co-op with my brother. Those games all lose a lot playing solo.

Magicka, if you can get past the myriad swarm of bugs and crashes.

Titan Quest Gold