As part of the Mind Screw, near the end of the game a fake Game Over message is displayed with the words "Fission Mailed" instead of "Mission Failed" and the game continuing in a smaller window. As an unaware player can easily die thinking it is a real Game Over screen; the term is used to describe failures of a higher level than normal, as well as the trope it named.
One of Raiden's lines. Popular for its Narm, as his tone suggests it's something for which he should be very proud.
"I need scissors! 61!" Explanation (spoilers)
One of the fake Colonel's codec messages after Arsenal Gear is partially infected with a virus. Popular for its absurdity. Used to parody people who post Insane Troll Logic on the Internet. Time Cube is a prime example of the type of thing that gets this response.
About half of Snake's dialogue is copying someone else.
A surveillance camera?!
A Hind D?!
"Hey, you're that ninja."
"You can't do that! The future will be changed! You'll create a time paradox!" Explanation
The Colonel yells this in Metal Gear Solid 3 after a Game Over or killing a character that appears in a chronologically later game. Used when someone does something that would mess with time.