Urban Terror
--- This is a first person shooter (FPS). Best free one I've seen.
Open Arena
--- A FPS game, similar to Quake 3, this one is actually GPLed.
Smokin Guns --- A FPS
game set in the wild west of the 1800s.
Linux Game Database
--- I haven't actually used this much, but it looks good.
The games listed above require no installation, just unzip and
play.
They are quite large, in the 500MB to 700MB range. They all use
the
GPLed Quake 3 engine so they can run on modest hardware.
ATI and Intel hardware acceleration is supported by Fatdog64 with
the
included open source drivers, but you'll get better performance
from
the propritary ATI driver if it supports your card. Make sure you
check
to see if the version in the pet repository supports your card before
installing. For Nvidia you'll need the Nvidia package or SFS
installed.
There are a few games in the package repository too.