Markus decided to reuse an old Commodere 64 Competiton Pro joystick, so he added a USB adapter to it. The retro joystick uses a simple interface over the D-SUB 9 connector, using one connection for each movement direction and one connection per button.
He used a PIC24FJ64GB002 microcontroller to translate the native joystick interface to the USB. The schematic and a small tutorial on how to build your own are available.
Via the forum.