Alien Arena is a freeware online deathmatch game with fast and furious action for Windows and Linux! The game runs on the CRX engine, and features modern effects such as real-time per-pixel lighting and shadows, GLSL shaders, ragdoll physics, light bloom, reflective surfaces and much more, while still being able to run on even modest systems. The game includes a built in, as well as external server browser and chat client. Players can look up their stats online, chat with other players, and become part of a growing community. .
The second best incarnation of Tech 3 engine (the first is the IW4, but thats commercial).