Flick stick
An alternate mode of using an analog stick on a game controller, for first person or third person 3D games. Flicking the joystick in a direction faces the character or camera in that direction. For instance, flicking upward will do nothing. Flicking left turns the character left. Flicking downward will turn the character 180 degrees.
Invented by Jibb Smart.
Should only be used on controllers with a gyroscope such as the Dualshock 4 and Joy-Con so you can combine with gyro aiming.
A valid criticism of flick stick is that it takes too much setup and is very brittle. A lot of work is required to get it working in only one game, and the same work will have to be done for the next game. Subtle changes in configuration can make flick stick less viable or non viable.
A simpler alternative to flick stick is a touch pad that only registers X-axis movement, such as this 3D printed controller.