AssaultCube is a FREE, multiplayer, first-person shooter game,
based on the CUBE engine.
Taking place in realistic environments, with fast, arcade gameplay,
it's addictive and fun!
With efficient bandwidth usage, it's low-latency and can even run
over a 56 Kbps connection. It's tiny too, weighing in at a
lightweight about 50 MB package available for Windows, Mac and
Linux. On the correct settings, it can even run on old hardware
(Pentium III and above).