Insomniac Games is a very busy development studio this year. After just announcing Resistance 3, they hit us with another one with Ratchet: All 4 One.
Ratchet: All 4 One will have 4-Player co-op, with players assuming the role of Ratchet, Clank, Dr. Nefarious, and Captain Qwark! The game is due out in the fall of 2011.