This is a variant I invented. This might sound like a crazy idea, so here it goes:
A player may choose, if they want to, to start a fire in a 2x2 grid instead of making a move. You can only do this once every 10 moves. Neither player could start a fire on the first move, and white may not start a fire on the second move, either.
When someone starts a fire, it must be set in a 2x2 grid, and it can NOT be on both the d AND e files. It has to be all on the kingside or all on the queenside.
When there is a fire, first there will be a fire alarm, telling the pieces to evacuate from that area. The fire alarm will be 4 moves long before the fire starts.
Pretend you set a fire in this grid of squares. There will be a "fire alarm" for the next 4 moves. Then, the actual fire will start. Any piece that is in that area will be burnt.
Optional Rule Extension:
The pieces will then call the fire department. It takes 2 moves for the firetruck to arrive, and in those 2 moves, any piece that goes into that area or through that area will be burnt. If the fire is set on the kingside, the firetruck will come from the queenside, and if the fire in on the queenside, the truck will come from the kingside. Now, it takes another 2 moves for the firemen to extinguish the fire. The firetruck will be parked next to the fire. For example, if the fire is on the kingside, the firetruck will be parked on the 2 squares left (in white's point of view) of the fire.
Now, any pieces that are in the place of the firetruck will be driven over. The firetruck will get in the way of the pieces for 2 moves while they are extinguishing the fire. Then, the firetruck leaves, and the board is normal.
If the same square (not area) gets burnt 3 times in the game, it gets burnt completely. There will be a hole on that square, and any pieces that move onto the square or moves over the square (except the knight) will be lost.
Those are pretty much all the rules to the game.