This is my first entry for the Hack Vornheim Contest. I am running a little late (contest deadline was July 27, 2011) but since I don't actually care about winning anything, I think that's ok. I'll be attempting option #3, "expand something."
Without further introduction:
In Vornheim, Large Chess is "A bizarre and repugnant indulgence," in which specially bred halflings act out a game of chess, dressed as the pieces they represent. In my campaign, these are the only halflings in the world.
Large Chess is a brutal blood sport. When a piece is captured, the capturing chessman delivers a single blow to the chessman being captured (who must accept the blow passively). If, after the blow, the captured piece is still able to stand, he can re-enter the game from the back rank.
The chessman are bred and trained to deliver a blow that is as debilitating as possible. Each piece has their own capturing move.
Pawns (Punchies): When capturing, a pawn throws a punch. One arm is disproportionately large and overdeveloped with an enormous bony fist. HD1, AC10, Damage 1d4, Speed 75% human.
Knights (Jumpers): These chessman must be able to jump over the heads of other pieces and so they have grotesquely muscular legs. For making captures, they wield a wooden cudgel. HD1, AC10, Damage 1d4, Speed 75% human walking. Can make 15' lateral or 8' vertical jumps.
Bishops (Kickers): Bishops deliver devastating kicks but their feet are broken and fused so often during training that they find it difficult to walk. HD1, AC10, Damage 1d4 (if using hit locations*, Bishops get a +2 bonus instead of a penalty for targeting an opponents legs) Speed 25% human.
Rooks (Splats): Rooks must hold a large stone block above their heads throughout the game. When making a capture they bring this block down on the opponent's piece with tremendous force. If a rook lowers his block for any reason other than a capture, he is removed from the game. HD1, AC10, Damage 1d8 but terrible at hitting moving targets, Speed 75% human.Can carry 150% what a normal human can.
Queen (Widow): Queens walk on 5' stilts and capture with polo mallets. If a queen falls from her stilts, she may be attacked by all opposing pieces until she regains her stilts or leaves the board. HD1, AC10, Damage 1d6, Speed 150% human.
King (The Coin): Kings walk on arm crutches and deliver powerful double legged kicks when they capture. When a game is lost the losing team's king is literally captured. Often, a king will be redeemed for a large ransom. HD1, AC10, Damage 1d4, Speed 50% human.
Chessman are born in pairs. It is considered disrespectful to your opponent to play with unmatched pieces and most leagues forbid the practice. As a result, any chessman whose twin is debilitated becomes unplayable. These leftovers can be purchased very inexpensively at the slave market.
Chessmen know nothing about the world outside of their game. If they are freed or if Large Chess is banned, they are sure to come to wretched ends.
*I use a hit location similar to Zak's except that I allow players to target specific locations with a penalty to hit.