Diplomacy (Steven Douthat)

Excellent strategy game this, closely based on the Avalon Hill board-game of the same name. The author (Steve Douthat) knows how to clone games properly though - the instructions on playing the game are not available on the disk, because they're proprietary to the board game. Even if you don't know how to play (and I certainly didn't) after an hour of mouse clicking you get the hang of it.