CP3S said:

Dead Island

It is honestly probably my favorite title released in the last couple of years, and definitely the best co-op game I've played since Borderlands, regardless of its flaws.

Have it. Just have to finish the Borderlands expansions with my NY co-op buddy (formerly zombiefriend).

Speaking of the which, how the heck did you get those uber-hard collect achievements on Claptrap's Robolution? I've had no luck getting the rare items and I've read online that it's quite a beast.