The Jewish Granny. This peice, if it reaches the opponent's half of the board (your opponent's "home"😉 it becomes immobile and cannot be captured. It cannot thereafter be moved or influenced in any way. One per turn the controller of the Granny gets to make a demand (not necessarly based on the game), and if their opponent refuses, they lose a pawn due to guilt instilled and incessant complaining. Prior to reaching the opposing half of the board the Granny moves one square in any direction, but only once every other turn due to alzheimer's and a bad liver.
The miner.
Basically the same as a bishop, but it appears after the 10th move of each player. The player choses which colour the miner will be and can appear on the board on one of the two starting spaces of the opponent's bishops...if they're vacated. (so if only the white bishop starting space is empty in your turn 10, you can only have a bishop on the white diagonals).
The pulsating knight.
Can only be capatured when on black squares. When it's on white squares it can not be captured. It can only capture when moving onto a black square.
The dire slag.
You can opt to make your queen "dire" by removing a rook you own from the game. Any piece taking your queen is automatically removed from the board as well.
King with wings
You can opt to remove 4 pawns from the game (your own pawns obviously) and the king can move 4 squares in any direction.
The "ex" . It's like the queen , but so fat it takes up four spaces . It impedes your pieces , but does nothing to stop the opponents pieces . It eats your pawns if they get anywhere near it . It can also randomly sap the energy from your bishops and knights , can turn them against you , and also removes your castle . It has a companion piece called the lawyer which is like a little vantrilloquist's dummy sitting on her lap . The lawyer's job is to change all the rules of the game randomly .
I'm designing a set based on this variation with this piece included . It will be served on you through the mail and you've no choice but to pay for it and play . (It's very expensive , and no rule book is included for this variation .)
The "fat friend". Your queen and the "fat friend" always move together. They may never occupy non-adjacent squares. If the fat friend is captured the queen must return to her starting location, and start her progress all over again. Aside from weigh the queen down and impede her movement, she does nothing useful. The queen may not move or give check through the two squares occupied by the fat friend.
The Highlander - there can be only one.
The knight (highlander) moves as per normal and can be captured by any piece, but the player's next move is to return the highlander to its original starting square.
The highlander cannot capture a bishop as it occupies holy ground. If the bishop is occupying the knight's starting square, then the highlander cannot return, and normal play resumes. If the bishop leaves the knight's starting square, the players next move is to return the highlander.
If a highlander captures a highlander, it is the end for that piece, as in the movie.
If the highlander's King is on the knight's starting square it is checkmate.