Nexuiz is a fast paced 3d deathmatch game project created online
by a team of developers called Alientrap.  It is based on the
open-sourced Quake engine.  Nexuiz is a standalone game that can
be played locally or over the internet.  It is completely open
source and actively developed.

Note: This SlackBuild just repackages the binaries (no compiling). The
"source" download is about 900M.