One (well two) cool chess variant would be chess two.
Rules:
-There are 2 chess board with the pieces at their usual position on each
board.
-Black Start to board 1 on the first turn and white start on board 2 on the
first turn.
-Both choose and then make their movements on the same time, with black
making the movement on board 1 and white on board 2.
-After they make the first movement, black now have to move a piece on
board 2 and white on board 1.
-Then on the 3rd turn, they change the boards will be moving again.
-And again, and again....
-Other rules works as normal chess.
WIN:A player win when they capture the king on one board.
ONE VARIANT: Same rules, but if a player win on both boards, he wins the
game, if each player wins on a one board, its a draw and they have to play
again.