I'd agree on "Aliens vs. Predator 1" playing as a marine. You've got good weapons... but it's dark, you're fragile, and the aliens are so damn fast. The game also semi-randomly places enemies so you can't be sure where most of them will be. You're on your toes most of the time, listening for the telltale screeches... or the chittering of small, hard-to-spot, instakill facehuggers.