The answer? Why it's Batman, of course. In Batman: Arkham City, the only thing Batman does better than field strip assault rifles like a boss is break bones - and he's not happy until he's broken all the bones there are. How did you think they created the various bone-snapping sound effects?
The following video which gives much insight into the foley process of creating the sounds for Batman: Arkham City. I've always found foley documentaries to be hilarious. It's so funny to find out the completely mundane and often ridiculous ways in which sound effect for movies and videogames are created.
Batman: Arkham City Game of the Year Edition is set for release on May 29th.