Prey, it may have been released back in 2006 yet the graphics still hold up nicely, the story is good, there are quite a few interesting gameplay mechanics (portals BEFORE "Portal" made them popular, gravity walkways (can walk on the path no matter where it may go), and spirit walking), controls are tight, and there is a versus multiplayer mode which I have yet to explore. Best of all you can get the game for a song nowadays.
