"First person shooter" computer game by Valve Software (http://www.valvesoftware.com).
Pretty much won every "game of the year" type award for 1998...
Designed using the CabalDesignProcess.
Uses a heavily modified version of the original Quake engine (from IdSoftware). It is one of the first person shooters to have a real and interesting story line. One of the first, perhaps, but beaten by about 4 years by a creature named Marathon, with literally hundreds of pages of text in its story. Too bad it was only for macs, eh? (though I guess now it's out for everything at http://source.bungie.org ) -- DanUznanski It's also good fun in deathmatch networked play.
The mod community for Half-life is very impressive.
Some of the mods include HalfLifeNaturalSelection and CounterStrike and DayOfDefeatCategoryGame