Urban Terror is a freeware multiplayer first-person shooter video game developed by FrozenSand. Originally a total conversion of id Software's Quake III Arena, FrozenSand released Urban Terror as a free standalone game in 2007 utilizing ioquake3 as a game engine.
Visit Urban Terror's website for more information about the game.
Have a look at the following video prepared by the Bellum to get a glimpse of the game style and pace.
Teeworlds is a free online multiplayer game, available for all major operating systems. Battle with up to 16 players in a variety of game modes, including Team Deathmatch and Capture The Flag. You can even design your own maps!
A fast-paced, futuristic FPS with RTS elements, pitting technologically advanced humans against hordes of highly adaptable aliens.