first
Sauerbraten (a.k.a. Cube 2)
Cube is a free game with no actual plot
Sauerbraten is the sequal of no plot thats basically the same exact thing
but the game engine -which is open source btw- extremely modifided to look...
AMAZING!!!!
some screen shots don't look as good as other
the other ones don't look as good do to textures
its also ingame level editing
just press 'e' and you enter edit mode
http://sauerbraten.org/
its also open source and has been ported 2 linux as well as mac
there is also AssaultCube
its based of Cube 1's game engine so it doesn't look as good
here is the website
http://assault.cubers.net/
its basically deathmatch really with bots or online
another one is Nexuiz
its pretty fun
its just like Quake 3 arena and open arena-quake 3 clone literaly
http://icculus.org/twilight/darkplaces/download.html
it supposed to use the dark places mod-an amazing looking mod
but i don't know to much about that
just to be sure download the mod from the link above
it uses a free version of quake 1 but plays like quake 3
http://alientrap.org/nexuiz/
the water
[a href="http://www.nexuiz.com" title="Nexuiz - Simple, Fast, Intense and Completely Free" target="_blank"][img src="http://www.alientrap.org/nexuiz/promo/nexuiz_promo_slogan_500.jpg" title="Nexuiz - A free open-source fast paced first person shooter that runs on Windows, Linux and OSX." alt="Nexuiz - Simple, Fast, Intense and Completely Free" /][/a]