But currently mine is Shell Shock Live, though I haven't really been playing it the past week or so. Music Catch 2 is up there as well. I like tank games so Shell Shock Live fits that and listening to the music on Music Catch 2.
My favourite game so far is The Last Castle. I like the game because it's fun, and you could play as one of the classics: A warrior, a mage, and a rogue. You play in a multiplayer game, choosing one of those characters and work together to defeat waves while protecting the castle. It's really fun.