Tremulous is the best free software FPS game I've had the pleasure of playing, and I'm not alone in this opinion. It also has a community growing up around it, which should aid not only in growing its popularity but also in continuing improvements.Good for id Software for freeing the engine, and good for Darklegion Development for what its developers have done with it. Give it a try. You'll like it.
Tremulous is a free, open source game that blends a team based FPS with
elements of an RTS. Players can choose from 2 unique races, aliens and
humans. Players on both teams are able to build working structures
in-game like an RTS. These structures provide many functions, the most
important being spawning. The designated builders must ensure there are
spawn structures or other players will not be able to rejoin the game
after death. Other structures provide automated base defense (to some
degree), healing functions and much more...
Player advancement is different depending on which team you are on. As
a human, players are rewarded with credits for each alien kill. These
credits may be used to purchase new weapons and upgrades from the
"Armoury". The alien team advances quite differently. Upon killing a
human foe, the alien is able to evolve into a new class. The more kills
gained the more powerful the classes available.
The overall objective behind Tremulous is to eliminate the opposing
team. This is achieved by not only killing the opposing players but
also removing their ability to respawn by destroying their spawn