In addition to a big, head-trippy singleplayer campaign, the upcoming Far Cry 3 will feature a fleshed-out four-player co-op campaign. It's more than your standard "kill the enemy waves" setup; FC3's co-op has a story, complete with four different playable characters.
There's the hardassed chick, the goofy older russian dude, the wiseass cockney (or some such accent?) criminal and the big tough action dude.
In this video, a Ubisoft representative walks us through the ins and outs of a couple of co-op missions. Cool.