Bweh

This is a top-down turn-based shooter. This works because of a momentum mechanic that forces players to think a couple of moves ahead. 
Mechanics:
Primarily point-and-click based (though keyboard is needed)

Turn based

Free-for-all, PvP or PvE

Players are shot when one moves to the same row or column

Players have momentum in the last moved direction

River which removes momentum, adding complexity

Obstacles cannot be moved or shot through

Randomly generated map of chosen size, characters placed on map by player

Bots can be placed alongside players, allowing singleplayer gameplay

8-bit (square wave) sounds

Completely local, ie multiplayer is local, occuring in one instance on one machine

Additional features
Option for instant respawn (rather than new round)

Option for hiding map behind obstacles (continuous or discrete, using tiles)

Option for "toroidal mode", allowing crossing of the edge of the map and appearing on opposite edge

Option for removing river