I'm gonna have to say either PlaneScape Torment or Arcanum... Both games rocked. PlaneScape Torment you're a dude who wakes up in a mortuary and has no recollection of who you are. A floating skull floats over and explains where you are and reads a message that was carved into your back. Arcanum is a game of magic versus technology. You begin on a zeppelin that gets attacked by airplanes, after crashing a strange gnome gives you a ring and tells you to 'find the boy'. Both excellent games I'd pick them up if you get the chance
