SkyCheckers

Sky Checkers is a multiplayer game that is influenced from an old kirby mini game. The objective is to knock your enemies out of the checkerboard using your weapon.

The last one standing wins. Some basic controls are that you move with the arrow keys and fire with the space bar. Of course, these controls can be configured.
Notable features include 3D graphics, bots with configurable difficulty, gamepad support, and network play (which uses port 4893 on UDP). This game is written in C and utilizes SDL and OpenGL.