BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
Cadaver is a simulated world of cyborgs and nature in realtime. The battlefield consists of forests, grain, water, grass, carcass (of course) and lots of other things. The game server manages the game and the rules. You start a server and connect some clients. The clients communicate with the server using a very primitive protocol. They can order cyborgs to harvest grain, attack enemies or cut forest. The game is not intended to be played by humans! Instead the idea is that you write artificial intelligence clients to beat the other artificial intelligences.
Wars of Destiny is a real-time strategy game. It is currently in a major building stage, but looks very promising. If you are interested in helping, then your assistance would be greatly appreciated. It uses SDL 1.2.0 and SDL_mixer, and it includes fully integrated network support for playing with other people over the Internet. It also includes a map creator and an easy-to-use interface for configuring WOD.
Scorched 3D is a modernization of the classic DOS game Scorched Earth ("The Mother Of All Games"). It incorporates a lively three dimensional landscape that includes animated jets, naval vessels, water, and even birds, in addition to detailed tanks and projectiles. Other enhancements include LAN and Internet play and music.