Check out BZFlag on SourceForge, a free multiplayer multiplatform 3D tank battle game. The name of the game stands for Battle Zone capture Flag. It runs on Irix, Linux, *BSD, Windows, Mac OS X and other platforms. It's one of the most popular games ever on Silicon Graphics machines.
Check out the web site for screenshots of the game.
BZFlag 2.0 'Falcor's Despair' is Released! (12/17/05@9:08PM)
The BZFlag developers are proud to announce that after much waiting and anticipation, BZFlag 2.0.0 is now available. BZFlag 2 introduces a slew of major new features making this probably the 'biggest' release in BZFlag's history in terms of development time put into it and features being added since the last publicly released version. Major new features include support for vastly more complex worlds, physics drivers, graphics improvements, weather (rain, snow, frogs), tank treads and tracks, animations, record and playback, new flags, new commands, optimizations and much more. There is a new central registration system, global ban list support, network, new cheat preventions, and network optimizations in place as well.