We've seen plenty of ways to use a Raspberry Pi as a retro game centre. However, if you really want to do it right, XodusTech shows us how to build that game console into a Game Boy.
The build here isn't easy by any means. It will require you to do some case modding to a Game Boy Pocket, desolder the Gameboy's button pad, rewire everything, install a new screen, take a few components off of the Pi, install a new sound chip and power supply, then get everything working together. The end result is a handheld gaming system you can load up with lots of old games. Head over to XodusTech for the full guide.