Paranoia. Not sure if there is any better game to divide and conquer players. Had a hard time playing this game with any of the groups I played with. I was never a big fan of playing it myself but loved the concept and reading the game material. It spawned tons of ideas on how to make things tougher on my players when I was DM'ing as well. For a game I really didn't like that I much I still hold this in pretty high regard for concept and design!
