Warhammer 40k: Space Marine
Only the Exterminatus cooperative mode has you and three other players fighting against increasingly difficult waves of enemy bots (similar to Horde mode in Gears of War 2, or Firefight in Halo: ODST). Exterminatus mode is not part of the base game, but it was released as free downloadable content, so that's a plus. One thing to keep in mind, however, is that there is a relatively small player-base for the cooperative mode at the moment (although the competitive portion is a bit more active, last I checked). And ever since THQ went bankrupt, and the license for this game was bought by SEGA, you can expect little to no future updates. That all aside, the campaign and cooperative modes are a lot of fun. I definitely recommend this game as a decent introduction to the grim darkness of the far future that is Warhammer 40,000.
Not at the current moment.