Halo or FPS Chess. 5-20 players each play one of the pieces on the board. Moves are taken without waiting for a turn. Only moves are legal that would be legal in a traditional game. Players can take black or white. After a player’s piece is taken, he must wait 1 minute and is respawned at a random location on the board. Scoring is done by who ever takes the most pieces. The piece you respawn as is randomly selected from the set of taken pieces.
Obviously this would only really work as a networked computer game.