Barrel roll

"Do a barrel roll!" - Peppy Hare, Star Fox 64 / Star Fox 64 3D

A barrel roll is a technique where a starfighter spins to deflect enemy fire. In Star Fox Command, the Arwing's G-Diffuser creates a gravitational field that allows the Arwing to collect items easily. In Star Fox, Star Fox 2, Star Fox 64, Assault, Adventures, and 64 3D, this maneuver is executed by tapping either of the shoulder buttons twice. In 64 and Assault, Barrel Rolls make the player turn or move faster if the roll is in the same direction as the ship's movement. Doing so is the only way to avoid one of Andross' attacks in both 64 and Assault. In Command, however, the player must make a circular movement on the touch screen to activate it. Barrel rolls only deflect basic laser-based attacks, as Smart Bombs, Predator Rockets, and rainbow beams from Gorgon aren't deflected.

Outside References

Google has stored an Easter Egg in its search engine, in which if you type "Do a barrel roll" in to the search terms, the whole page will rotate 360 degrees clockwise.
The popular game by Valve Software, Left 4 Dead 2, has an achievement that can be unlocked called 'Barrel Rolled', a clear reference to Star Fox 64.
This technique is described incorrectly in-game. What the game refers to as a barrel roll is actually an Aileron Roll.
Due to the numerous times it is mentioned in Star Fox 64, one of Peppy's phrases, "Do a barrel roll!" has grown extremely popular on the internet.