EvilSelf's Army of Two Review here.

Army of Two: 40th Day - You cant go wrong with the second installment of Army of Two. Same game mechanics, more of the same so to speak.

Gears of War series - If you are looking for a great cooperative shooter with a decent story look no further than Gears of War series - tons of fun and great characters.

Borderlands - outstanding co-op FPS with RPG elements, even though it lacks in an engaging story. It will provide you with hundreds of hours of gameplay.

EvilSelf...