Controllers!

ControllerMate is a controller programming tool that allows you to customize the behavior of your HID devices — keyboards, keypads, mice, trackballs, joysticks, gamepads, throttles, among others. ControllerMate’s philosophy is to be as flexible as possible, to provide a set of basic programming tools, and to allow the user to combine those tools in an endless variety of ways.

Joystick Mapper is an Mac OS X application that allows you pro play any game or use any other application with a Gamepad or Joystick, even the ones without built-in support.

The USB Overdrive is a device driver for Mac OS X that handles any USB mouse / trackball / joystick / gamepad / media keyboard and any Bluetooth mouse from any manufacturer and lets you configure them either globally or on a per-application, per-device basis.

Available exclusively on the Mac App Store. GamePad Companion 3.1 is a utility that makes it easy to configure your GamePads (controllers, joysticks, etc..) to play your favorite OSX games. You can configure your controller to work as your mouse cursor and buttons, or to map to any key on your keyboard, and you can save your layouts for the next time you want to play your favorite game!