As difficult as it may be to conceive, the same Bit Fix Game Boy Classic modding competition that brought us the Game Boy mini-fridge, aka "Cold Boy," has also produced ... the Guitar Boy. And yes, it's exactly what it sounds like.
Created by Fibbex, it's both a working electric guitar and an oversize Game Boy. The latter is run by a Raspberry Pi B+; the A and B buttons on the body are gaming controls as well as volume and tone for the guitar.
You can see the Guitar Boy in action in the video below. Fibbex has also shared build photos.