Here are some "chess" idea's that took me a while 15 minutes to think of a couple of months ago. Since this board is here now, I'll post there here now!.
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Froggy Chess:
1/2 of the pawns are replaced by froggies. They are placed on every other space along with the pawns (froggies go on the white squares). They can only move 2 spaces forwards, 2 spaces backwards, 2 spaces to each side, and 2 spaces diagnal. They can "jump" over other pieces. If they land on another piece, they capture it! (just like normal chess)
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Camando Chess:
Before the game starts, each player picks a secret "camando" pawn piece. This piece can not be captured by other pawns. If another pawn tries to capture it, the attacking pawn is then "captured". (and then the other person would know which pawn is the camando pawn.)
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BrainKing Chess:
The King is replaced by a BrainKing. After the 10th move, the BrainKing can move on top of one of it's own pawns and promote it to any other piece! That promoted piece then sits next to the board and can be placed into play the next turn (like Loop Chess). After the BrainKing "upgrades" one of it's own pawns, it can AGAIN promote another pawn after another 10 moves.
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Bully Pawn Chess:
All pawns are replaced with Bully Pawns! The thing this pawns can do is they can actually "push" back another pawn a space. So take for example you have a pawn at A5, and the other person has a pawn at A6. Your pawn can "push" the A6 pawn back to A7 - letting your pawn take over the A6 spot.
Other rules: If another piece is behing the pawn, it can not be pushed (since the space is already taken). The Bully Pawn can not push any other piece - just other Bully Pawns of the opposite color.