There are lots of ways to mess with the rules of chess. You can play it on a board of hexagons, for instance. But you can do quite a lot to freshen up the game without needing any special equipment. Change one or two rules, and you have a whole new game. Here are my top ten suggestions for chess variants that require no special equipment, just a standard board and pieces.
Berolina Pawns. Normal pawns move straight forward and capture by moving diagonally. Berolina pawns are just the opposite — they move along the forward diagonals, and capture by moving straight forward. I like the idea of “Berolina plus” pawns, which add the ability to capture by moving sideways. Like normal pawns, a Berolina pawn can optionally move two squares on its initial move, and is otherwise restricted to moves of a single square. Berolina pawns are a simple idea that completely transforms the opening.
Scorpion Pawns. In addition to the normal pawn movement and capture, scorpion pawns can make a non-capturing move like a knight, but forward-wide only. A pawn on e4, for instance, would have extra moves to c5 and g5. Scorpion pawns are dangerously maneuverable.
Cylindrical Board. The left and right edges of the board are considered to be joined to one another. A rook on a3, for instance, can move to the left and arrive on h3. A cylindrical board has no center — or rather, the entire 4th and 5th ranks are the center. Advancing the rook and knight pawns in the opening, rather than the king, queen, and bishop pawns, becomes sensible, and castling makes little or no sense.
Contagious Knights. Any piece that is protected by a friendly knight gains the extra ability to move and capture like a knight. This variant can be played either with the knights operating like normal pieces, or with knights that can neither capture enemy pieces nor be captured.
Reflecting Bishops. On reaching a square at the edge of the board, a bishop can bounce like a billiard ball, continuing its move on a diagonal at right angles to the start of its move.
Rook Catapults. During its normal move, a rook can “throw” the friendly piece most nearly behind its starting square “over its head,” so that the other piece lands on the far side of the rook’s destination square. Several variations of this idea are feasible. The rook might be required to catapult the piece behind it, or the catapult might be optional. The catapulted piece might land on the square immediately past the rook’s destination square, or it might travel further along an unobstructed rank or file. The rook catapult would probably have little or no effect on the opening of the game, because a rook has to have made one or two moves before it’s in a position to catapult anything.