Zeno Clash (PC)

This is a very unusual game with strange, surreal visuals, and a confusing story, yet it's also strangely interesting.  Zeno Clash is filled with odd-looking creatures, and a pre-industrial punk-like sensibility.  It's a first person action game where you spend a lot of your time punching and kicking enemies, though there are still times where you can use firearms.  The game is very short (only 4-ish hours), but it certainly is an experience.

Bulletstorm (PC)

I wasn't hugely interested in this game when it first came out because the juvenile language and general attitude that I got from the game looking at its trailers was a big turn off for me.  However, I eventually picked it up at a Steam sale for next to nothing, and the game was alright.  I'm certainly glad that I didn't pay $60 for Bulletstorm, but there was a bit of fun to be had, and the trick shots were kinda neat.

Hard Reset (PC)

Looking for an FPS with a decent single-player experience, and placed in a futuristic setting?  If so, you may want to try Hard Reset.  It's pretty darn good.  There's even a demo, so go check it out. =)