5. Fallout (series)
You didn't really think that a game based in post-apocalyptic America was going to come off as squeaky-clean, did you? The whole Fallout series was violent — you just couldn't see as much in the original games when you reduced enemies to a fine, red mist. But when the series hit 3D in 2008, Fallout 3's huge open world, over-the-top violence, and inky black humor catapulted it on to many lists as one of the best of last year.
Gore factor: Five pints of blood. Firing your weapon into a crowd and watching chunks fly in this game actually makes you laugh and cringe at the same time. A steam-powered bolt-launcher emits a cute whistle sound while it rips people apart. A nuke launcher dings as if the turkey is done cooking. And one of the special abilities you earn in the game is "Bloody Mess." I'll let you figure out the rest. One interesting side note, though: Like Grand Theft Auto IV, Fallout 3 didn't force you to use violence. You can actually get fairly far in the game without having to resort to violence all the time. As if.