If you've turned your media centre into a video game console but the new school controllers just don't invoke the same feeling of nostalgia, you can easily turn an old NES controller into a USB gamepad with an Arduino.
This project requires the usual tools one would expect from an Arduino project: a soldering iron, a multimeter, electrical tape or heat shrink, and a few other basic tools you probably already have. You'll also need an Arduino and a specific set of resistors, diodes, and a spare USB cable that you don't mind cutting up.
The project essentially involves hooking up the pad to the Arduino and having it run a special sketch that causes it to show up as a USB joystick. The instructions also show you how to fit all the electronics inside the gamepad, so you don't end up with any loose circuit boards or wires. It's not for the inexperienced, but a cool project if you're serious about that old school controller feeling. Hit the link for the full instructions.
Convert an NES Gamepad to USB with Arduino [Instructables]