I enjoy hacking and modding things for my own evil plans, however, someone has done something more extreme than I would probably care to try. Build a PS2 Guitar Hero controller from scratch.
Video after the jump
What is great is that the guy didn't just show up with a cool guitar and leave it at that, he also put together an Instructables guide. You'll need quite a few spare parts lying around to pull this one off. Two PS1 controllers, a tilt sensor (which can be made from another Instructables guide) and a whole lot more.
In the end you're left with a controller that is fully capable of rocking out to both GH1 and GH2. While it may not look like it will win any awards for best-looking guitar, you can still call it your own. Besides, you're building the whole thing yourself, you can make it look however you want!
How to make a PS2 Guitar Hero controller out of scratch [via instructables]