This week Damnation, a steam punk meets western action game, hits the Xbox 360, PlayStation 3 and PC. What sets Damnation apart from other shooters is the game's verticallity. That is, the levels are designed to be more up and down, not just front to back.
The two player online co-op allows players to jump in at anytime to help their friends through the story.
You can snag all three versions from Amazon, supporting Co-Optimus. Or you can snag the PC version via digital download from services like Steam.