Most people know that the wired controllers for the Xbox 360 can simply be plugged into a computer and used to play games, but the original Xbox controller can do the same with a little work. I've known for years (since I first researched Xbox modding and installed XBMC) that my old non-360 Xbox controllers were using USB, but Microsoft had changed the plugs on the ends.
I knew that by cutting off the plug at the end of the breakout cable and replacing it with the end of a USB cable the controller could be used on a computer, with an appropriate driver, but this would make the controller unusable on the Xbox. It wasn't until recently that I decided to do this myself and found out that you don't have to give up an Xbox controller to get a PC gamepad. By soldering the USB plug to the controller cable you can make a controller that works with a computer and still works on the Xbox.
Here's the guide I used: link
The end result: keyboard-free emulators! I can play Sonic on my computer without having to buy a gamepad or use the keyboard. It's a nifty bit of recycling, since I use my Xbox almost entirely for XBMC these days, it's nice to be able to use those old unused controllers for something. Plus, it's an easy way to gain a little experience with soldering.