PWC: When a capture is made, the captured unit (except a King) is replaced on the square the capturing unit just leaves. A Pawn is immovable on its 1st rank.

Madrasi: Units, other than Kings, are paralysed when they attack each other. Paralysed units cannot move, capture or give check, their only power being that of causing paralysis.
Madrasi RI (rex inclusive): the rule applies to Kings as well, so the two Kings may stand next to each other.

Alphabetic Chess: The squares are considered in the order a1, a2…a8, b1…b8, c1 and so on to h8. At each turn, only the unit standing on the square which comes earliest in this order may move. However check and mate are normal.

Grasshopper(G): Moves along Q-lines over another unit of either color to the square immediately beyond that unit. A capture may be made on arrival, but the hurdle is not affected.

Kangaroo(KA): Moves along Queen-lines like a Grasshopper, but over 2 hurdles (which may or may not stand on adjacent squares) to the square immediately beyond the second hurdle. A capture may be made on arrival, but the hurdles are not affected.

Fers(FE): (1,1) Leaper.