First-person shooters: future, present, past
First-person shooters is a pretty straightforward subgenre of action games. Gameplay mechanics are simple and straightforward: run away from enemies, shoot them, find items and power ups and go on.
What I always liked in FPSs was the variety of theme/setting from game to game. Here's a few examples. Spear of Destiniy (yes, it's Wolfenstein) was set in the past, TekWar, In Extremis and The Terminator: Future Shock were set in the future, and there's also something set in the present (with a sci-fi twist): Redneck Rampage.