WITCH – One of the Special Infected types in the Left 4 Dead series. The G-Man – A mysterious recurring character in the Half-Life series. The Freeman – The nickname Gordon Freeman is given by the Vortigaunts of Half-Life 2. 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.