The Konami Code is a secret cheat code used in many Konami video games. At some point during the game, the player would press:

Up Up Down Down Left Right Left Right B A

and some sort of secret option would be enabled.

There have been other variations of this code as well. In an SNES game of the Gradius series, one must use the controller's "L" and "R" triggers while the game is paused. Using the directional pad buttons instead of the triggers would cause your ship to explode. In a Playstation 2 version of the Gradius games, the "square", "triangle", "X", and "circle" buttons are used as substitutes for "B" and "A" in the traditional code.

The most famous use of this code was in the classic NES game Contra. Use of the code dramatically increased the ease of playing the game, raising the player's "lives" from 3 to a much more generous 30. Only seasoned "pros" could finish many Konami games without the use of the Konami Code. Ask a game fan that grew up in the 1980s about the Konami Code, and they will most likely still be able to recite this code from memory.