6. Adam Mcintyre Fight - Dead Rising
The psychopaths in Dead Rising vary from "douchebag with a gun" to "totally crazy maniac", but Adam the clown is hard to classify. His high-pitched voice, the face he makes when "crying", his chainsaw-juggling - everything that can be wrong with clowns, Adam has it. Fighting him can be frustrating (the area is small, and even moving through the halls, you have so little space to maneuver), so you just want to end it quickly, because when he approaches, it's plain terrifying. Even when he dies, you can't achieve some peace: just remember how he died...how he laughed until the very end. That will haunt your nightmares.