Alien Arena is the best free downloadable game on the net

Alien Arena is a 3d first Person Shooter.The objective of this game is to
kill as many aliens as possible within 3 min. You begin with a colt 45 pistol
as you gain credits from killing aliens you will be able to buy better weapons
from the weapon store. The better the weapon the easier and faster it is to kill the
aliens resulting in a better score. after each three minute session in an arena you have the choice
of submiting your highscore to the online highscore board the highest score is the champion.