Valve Software/Memes

Valve Software games are particularly good at spawning memes. In fact, Portal and Team Fortress 2 now have their own pages, but there's plenty in some other games, and the company itself.

Half-Life:

 * "HAAAAAX!"
 * Garry's Mod has the HAAAX! gun. It summons the scream then throws a computer monitor at the target. In slow-motion if cheats are enabled.
 * (The HAAAX! gun being based off of the actions of the aformentioned Dr. Hax)
 * "I still have nightmares about that cat..."
 * "Don't forget to reload, Doctor Freeman!"
 * "Rice."
 * "Pick up that can!"
 * How Do I Shot Web?
 * Adrian Shepard from Opposing Force is an Ensemble Darkhorse Valve has been meaning to get back to including in the series. However in the interim, another series has sprung up with a lead also named Shepard. Cracking jokes about Adrian becoming Commander Shepard is fairly common.

Left 4 Dead:

 * The Hunter wants to be Altair.
 * "I hate small towns." "I hate planes."
 * Louis is GRABBIN' PEELZ!
 * BUTTLOAD OF PILLS.
 * "I ever tell you about the time when me and Keith..."
 * [X] startled the Witch! (Where x is, say, Nature, or Zoey.)
 * Entering the storage room....of love. Picking up the katana....of love.
 * WUBUBU
 * Karma Charger is watching you...
 * "No zombie is safe from Chicago Ted."
 * Coach's chocolate helicopter.
 * Both the Peek-a-boo Charge (or Jack-In-The-Box Charge) and Piñata Time are growing in popularity.

Counter-Strike:

 * Boom! Headshot!!!!
 * "DOOR STUCK! DOOR STUCK!"
 * "Terrorists Win."

Day Of Defeat:

 * TELEFONMAST!

Other:

 * Whenever someone calls Gabe fat, he delays Episode Thr-... GODDAMN IT
 * "Worth the weight."
 * "Wow, this (Insert name of obese game character) looks like Gabe Newell."
 * "BOOMER!"
 * "Valve Time"
 * Meanwhile, at Valve..... [Insert nonsensical Valve-related image, or image of people - usually Gabe - slacking off]
 * Creating absurdly deformed faces in Garry's Mod by turning the facial muscle sliders way past where they were meant to go, or in combination with others they weren't meant to be combined with. Very popular in Garry's Mod based videos.
 * Gabe's Watching
 * GABEN
 * G-A-B-E-N
 * "Uhh, no. It's just me, Gabe Newell."
 * "Valve Can't Count To Three"