[http://www.nexuiz.com/ Nexuiz] is a first person online shooter. Its license is under GPL!
Download
You can download it from the [http://www.liflg.org/?catid=6&gameid=64 Loki webpage]
Installation
Install Nexuiz with the following command:
sudo sh nexuiz_1.1-english-2.run
Start
Star Nexuiz with the following command:
nexuiz