So what is Alien Arena?
If you're a gamer but not familiar with Alien Arena, think of Quake III or Unreal Tournament and you won't be far off the mark. If you're not familiar with those icons of the first-person shooter genre, think massive, sustained, unrelenting, ankle-deep-in-blood, kill-or-be-killed carnage which can be enjoyed solo, just you against the bots on your PC, or, if your taste in killing tends toward living targets, in multiplayer mode on a network server. - Source
If nothing else download it and give it a try. What can it hurt?