Co-op PC game suggestions

[Ensam]

Helllllllo BG!

I'm looking for some suggestions on games that allow co-op more or less for the story mode. FPS preferred but willing to try new things.

Campaign in Left 4 Dead series is best example I can give of what really I'm looking for.

Something like Warcraft 3, with being able to do online 2v2 matches, are also cool.

I don't know that many games, so any help you can give is much <3

Preference towards free (or ability to play together with crack) games

[Cayos]

Borderlands is pretty fun, kind of a mix of an RPG and a FPS.

[dejet]

Second borderlands, I have not done much coop but people say good things. Have had fun witht the little solo play I have done.

[Insanecyclone]

http://www.co-optimus.com/system/4/pc.html

[Ensam]

Thanks! :D

[Lucavi]

A shame there aren't many racing co-op games on PC anymore. Seems the age of having 2 buddies playing together in something that doesn't involve shooting people have long since passed.

[Recaldy]

Sven CO-OP mod for the original half life is my favourite. Simple controls for alot of fun and variances in tasks and maps. Worth it for about 1-2 gigs total with character "customization" and almost endless amounts of maps and custom content. Best thing? It costs 10$ on steam. (Hal Life needed to play Half Life mods) My favourite thing on some servers is the XP mod.