Joi enables you to play games with a gamepad/joystick that did not originally support one. This works by emulating the keyboard. Just plug-in your gamepad and start Joi. Then all you have to do is map the keyboard keys to the axis and buttons you want for your gamepad. Joi can be used to play online games and even run behind fullscreen games on the Mac.
Joi supports gamepads that are supported by Mac OS X. Other gamepads that are not supported may work but are not officially supported.