The Combine – The primary antagonists of Half-Life 2 and its episodic sequels.TAAAAANK! – A warning shouted by the Survivors in the Left 4 Dead series when a Tank is spotted.Still Alive – The name of the song played during the end credits in Portal.

One-Man Cheeseburger Apocalypse – A reference to a quote from Coach in Left 4 Dead 2.IvanTheSpaceBiker – A nickname given to the original model of Gordon Freeman in Half-Life.Hostage – A hapless citizen held up by the Terrorist team in Counter-Strike.GLaDOS – The main antagonist of Portal.Dog – The name of Alyx Vance's pet robot from Half-Life 2.Delicious Cake – The 'reward' of subsequent testing in Portal.Crowbar – Gordon Freeman's melee weapon of choice in the Half-Life series.Companion Cube – An object in Portal used to solve Test Chamber 17.Chell – The name of the protagonist of Portal.CEDA –- The Civil Emergency and Defense Agency in the Left 4 Dead series is responsible for control of the Infection.Boomer Bile – A substance produced by Boomers in the Left 4 Dead series.Black Mesa – The main setting of Half-Life.Aperture Science Prototype XR7 – Aperture Science Laboratories is the main setting for Portal.Some bots which have names that reference other games include: Should a player contribute enough to obtain 200 stamps for their World Traveler's Hat, its rank will change to ' Unobtainium', a reference to a recurring alloy in science fiction and speculative science. The effect will only be visible while on a map that has been donated towards! Given to generous souls who have donated to community map makers.

Left 4 dead 1 parody