Invented by John Gallicano and Steve Mann in 1997. The rules are almost identical to ordinary chess, except that any piece may "capture" onto a square occupied by one of your own pieces, removing that friendly piece from the board (capturing your own king this way is the one thing not allowed). Clear a blocked path, thin out your own position, or find uses nobody saw coming.
Simplifications: en passant and castling are omitted. Check and checkmate aren't enforced — capturing the enemy king directly ends the game.