You've probably already heard this from everyone, but this game is fantastic. My only complaint is that if I spawn near the first guy in the first round, then I seem to instantly die before the second round even starts. Two times this happened to me, which isn't a lot, but it's weird that it happened twice.
The art style and animation are funny and really cool, music isn't particularly interesting but stays out of the way of what you're really listening to, which is the gunfire. The game mechanics are so simple but so well-done, and the addition of a leaderboard is the final touch to keep bringing you back for more.
Bravo!