bzflag

BZFlag is a 3D multi-player tank battle game that allows users to play against each other in a networked environment. There are five teams: red, green, blue, purple and rogue (rogue tanks are black). Destroying a player on another team scores a win, while being destroyed or destroying a teammate scores a loss. Rogues have no teammates (not even other rogues), so they cannot shoot teammates and they do not have a team score. There are two main styles of play: capture-the-flag and free-for-all.