6. Gears of War (series)
Lock Michael Bay, Jerry Bruckheimer, and James Cameron in a room and tell them to make a summer blockbuster-caliber sci-fi action game. Epic Games beat them to it. The Gears of War series has done a gruesome job of bringing the cave-dwelling Locust menace to life in this over-the-shoulder shooting gallery. And the series, though maturing by trying to develop an honest-to-God plot with pathos, is still a bloody affair.
Gore factor: Three pints of blood, extra chunky. Two words: Chainsaw Bayonet. The most ingenious invention of "modern" warfare is also one of the most effective — and satisfying — ways to mow through the hordes. Strap a chainsaw to the end of an automatic rifle. By the time you hear it's grinding roar and see the camera zoom in, you know something messed up is about to go down.