One of the best games in existance. Despite subpar graphics, this game, created by Dynamix and Sierra, is very easily modded (not to mention pirated), and at one point, was considered the BEST MMOFPS out there. Free online play. irc.tribes.net for some more info. Full name: Starsiege: TRIBES.
Those guys in tribes version 1.08 screamed "AURR!" in a squeaky nonhuman voice when they died... Hahahaha..."