Quake III Arena
Quake III Arena is a first-person shooter developed by id Software in 1999. Unlike the previous games in the Quake series, it focuses on competitive multiplayer action without any traditional singleplayer plots. The singleplayer mode is played against bots like in Unreal Tournament, a similar computer game done by Epic Games in the same time. Quake III Arena has been officially released for Microsoft Windows, Apple Macintosh, Linux, Sega Dreamcast and Sony PlayStation 2.
In 2000, id Software published an expansion pack called Quake III Team Arena featuring new game modes, weapons, items and player models. In 2005, they released the source code under the terms of the GNU General Public License, so several mods and games based on the engine were done, like Tremulous and OpenArena. In 2010, id Software released Quake Live, a free browser-based version of Quake III Arena.
In this video, you can see the playable demo of the original game. I haven't played this game for ages, so someone might be better than me :P