Create a Joystick Using the Arduino Joystick Library 2.0 : 12 Steps (with Pictures) - Instructables
Arduino Joystick Shield
I made a gaming control panel using an Arduino Leonardo to play simulators. Currently using it for DCS World, but it should work in most games just like any joystick / gamepad.
DIY Joystick Game Controller using Arduino Leonardo and Joystick Module
DIY Joystick Game Controller using Arduino Leonardo and Joystick Module