Nintendo/GameCube

Recalibrate the Controller
Recalibrate the Controller in one of the following ways:
 * Push RESET (or turn the system OFF and then ON) while making sure to not touch the control stick. This ensures the control stick is in the Neutral (center) position.
 * Press the X, Y, and Start/Pause buttons simultaneously for three seconds during game play, making sure to not touch the control stick. This ensures the control stick is in the Neutral (center) position.
 * Unplug the controller and re-insert it (while the system is ON).

Source: | Nintendo - Customer Service | Nintendo GameCube - Accessories