BZFlag

BZFlag is a free online multiplayer cross-platform open source 3D tank battle game. The name originates from "Battle Zone capture the Flag". It runs on Irix, Linux, *BSD, Windows, Mac OS X, and many other platforms. It's one of the most popular games ever on Silicon Graphics machines and continues to be developed and improved to this day. It's one of the most popular open source games ever.

The source code to BZFlag is released under the GNU Lesser General Public License and is freely available to anyone.

BZFlag is primarily written in the C++ language, but does contain some modules written in Perl, PHP, and Python.

Head spawns to the head of the table for six

c3po destroys a guided missle shooter with grace and style

Dinner for six mayhem and destruction, the Mad Hatter is ready to take someone away

http://www.bzflag.org/