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.
One of the lines spoken by civilians when the manhacks show up; has become a standard response to players who appear to be cheating in any game. Gained new life when machinima-maker Bo Schitt created recurring character Doctor Hax.
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)
From the introduction of Half-Life 2, part of the G-Man's monologue to Gordon Freeman. The original line is "Rise and shine, mister Freeman. Rise and... shine."
"Pick up that can!" Explanation
In the introductory level of Half-Life 2, a Combine officer stops you momentarily near a trash can, knocks over an empty can and orders you to throw it away. You can either oblige to the order or throw it at him, but either way you advance.
Natural Selection, a mod for Half Life, has an alien which can create webs; one hapless noob had his confused utterance immortalised. Often coupled with an image of Spider-Man, and used in any situation in which someone doesn't know how to operate something.
One of the Special Infected, the Hunter, has the ability to jump around from place to place. This mechanic is similar to Assassin's Creed, and there's also the similarity between the Hunter's hoodie and Altair's hooded cloak.
One of Francis's Catch Phrases has him professing his hate for parts of the level. Flanderized to the point where the only thing he doesn't hate is vests.
Louis is GRABBIN' PEELZ! Explanation
One of Louis' lines from the game. Has mutated to suggest that Louis really likes pills.
Ellis often tells stories about his friend Keith, who has gained Memetic Badass status. Normally invokes Rochelle's reply of "Ellis, honey, can this wait?" or Nick's reply of "Ellis, is now the best time?"
[X] startled the Witch! (Where x is, say, Nature, or Zoey.) Explanation
One of the Special Infected, the Witch will leave the player alone unless pissed off (which is very easy to do). When that happens the message "[player name] startled the witch" comes up.
Entering the storage room....of love. Picking up the katana....of love. Explanation
One of the locations in Left 4 Dead 2 is a Tunnel of Love. While in the tunnel, the characters in the game will refer to found weapons as "[weapon name] of love" rather than simply "[weapon name]."
One of the Special Infected, Chargers seem to have a nasty habit of turning up whenever a player does something overconfident or dickish. Thus, they gain the name "Karma Chargers". Also helps that one of their vocal grunts sound something along the lines of the aforementioned term.
"No zombie is safe from Chicago Ted." Explanation
Left 4 Dead's story is largely told through graffiti left on the walls by previous NPC survivors. One of them, calling himself Chicago Ted, left the above note in the final saferoom before the finale of "No Mercy."
Coach's chocolate helicopter. Explanation
In L4D2's intro video, Nick teases an exhausted Coach that the rescue helicopter might be made of chocolate. "Chocolate Helicopters" happens to be the name of the music playing when he said that.
Both the Peek-a-boo Charge (or Jack-In-The-Box Charge)*
A player-controlled Charger waits behind a door players have to open, then strikes as soon as they do so
and Piņata Time*
A Boomer spews on a player as a Smoker ties them up and dangles them in the air for the Common infected
Counter-Strike, while not the first game to reward headshots, was the first to add a meaty thwack! sound when pulling one off. Then CS became the most popular mod ever, cementing the idea that headshots were supposed to sound like that and here we are. FPS Doug is the Trope Namer.
A video where one player gets wedged between a half-open door and another player.
"Terrorists Win." Explanation
The two sides in Counter-Strike are Terrorists and Counter-Terrorists. When one of them wins the round, the gruff announcer says "[Counter-]Terrorists Win". Someone animated the collapse of the World Trade Center in the Source engine, and used this as the punchline.
Gabe Newell is the co-founder (and face) of Valve. Valve is notorious for Schedule Slip with all of their titles, and Half-Life 2: Episode 3 has seen the worst of it, especially since they started the episodic content with the justification that they could release titles quicker. Many years later, and there's no evidence that they even started on Episode 3.
"Worth the weight." Explanation
More Gabe Newell fat jokes, emerging from the TF2 commentary. The original line is "...after nine years in development, hopefully it will be worth the wait."
"Wow, this (Insert name of obese game character) looks like Gabe Newell." Explanation
Jokes about his size are rampant.
"BOOMER!" Explanation
Boomers are a horribly obese Special Infected in the Left 4 Dead games. The comparison was inevitable.
The standard answer for when anybody asks when the next Valve-related product is going to be released, related to both Schedule Slip and Vaporware. Half-Life 2: Episode 3's release date is apparently pegged as "Coincident with the Rapture."
Meanwhile, at Valve..... [Insert nonsensical Valve-related image, or image of people - usually Gabe - slacking off] Explanation
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.
Something of a meme on boards such as Steam Forums and Facepunch.
GABEN Explanation
A meme resulting from Gabe Newell's email address, gaben@valvesoftware.com, said at the end of the first commentary piece in Team Fortress 2's commentary maps. It is pronounced "Gabe N.", which sounds like "Gay Ben", and is sometimes used in the latter context.
G-A-B-E-N Explanation
For one of the Portal 2 commentary nodes, instead of pronouncing his name on the email address he spelled it out (maybe because of the above?).
Even though they're juggling more than half a dozen properties at this point, none of the games have received a proper third installment. And which episode of Half-Life 2 is being delayed absurdly long, even by Valve standards? Episode Three, of course.
