When Batman is out of the city, the Impostors will play.
http://www.gothamcityimpostors.com/game-information/Release Date: Jan 10, 2012. Price: 15$ Platform: Xbox, PS3, and PC
http://www.youtube.com/watch?v=GTBgZybSLGg&feature=relatedWhile Batman is gone doing.. who knows what. The Jokerz, a group of criminals rampage the city in a deadly crime spree. However a group of people, inspired by Batman's vigilante but unable to take the 'honorable' nonlethal apporch, take the fighting to the Jokerz. These Batman wannabees simply know as Bats, fight as the last defense to an unprotected Gotham City.
Anyway this is actually a pretty fun shooter that gives you a ton of customization options and weapons to work with. One second your using a bear trap, the next a jack in the box explosive. They are starting an open beta soon so if you sign up you can get a chance to try it out before it comes out on January 10 for 15$.