The Dabaaba
The Dabaaba is a piece from ancient Chess variants, and leaps two squares Rookwise.From e4, a Dabaaba can reach e6 (even if there is something on e5), g4, e2, or c4; but notice that a Dabaaba can never get to 48 of the 64 squares on the board: there are four different "colors" of D.
By itself, the Dabaaba is too weak a piece to be of much interest, but its power can be combined with the powers of other pieces to make new and interesting ones. By itself, it is worth little more than a Pawn, but in combination with other pieces it is worth half a Knight, more or less.
The funny notation for this is simply the letter D, because the Dabaaba is one of the basic geometric ingredients used in the recipes for other pieces.
It would be possible to have a D7 piece which would be to the D what the Rook is to the W. This Dabaaba-rider piece could go from a1 to a3, and if a3 was empty it could continue its move to a5, and if a5 empty, and so on. Because a D7 would already attack an enemy pawn without the need for any developing move, I do not yet use it in any of my games.
The Pawnless endgame with King plus four D (of different "colors") versus King is an easy checkmate.