This week and last week, i have been trying to download several 3D games for Linux and i tried to played them on my new desktop. I have downloaded Assault Cube, Nexuiz, and Alien Arena. Those three games are FPS-based game, so if you are familiar with Counter Strike, then you will not have problem playing it.
The three of them doesn't need to be installed, as it comes with a wrapper script to execute the game. In case of Assault Cube, you may need to install openal which is available through SlackBuilds project. Also, don't forget to install VGA driver in order to enable 3D acceleration. I used NVidia on my desktop.