Sure, you can pick up a used Gameboy for about $20 bucks over on eBay these days, but why buy one when you could build one for yourself?
Matt over at Liquidware decided to build an “open source Gameboy” (known as the Gamepack) using off-the-shelf parts, including the modder-friendly Arduino microprocessor. While the Arduino may provide the brains of the operation, the 128×128 TouchShield Stealth color OLED touchscreen is most definitely the soul. Rounding out the build is an Inputshield board, which provides a tiny joystick (complete with rumble) and control buttons as well as a flat Lithium battery pack.
The Gamepack system is now available in kit form so you can build one for yourself. At this point, the Gamepack only runs some rudimentary homebrew demo code, but the hope is that others who grab the kit will contribute more advanced games, or maybe even a Nintendo emulator.
At $249 for the Gamepack kit, you could buy more than 10 used Gameboys. But none of them would be nearly as cool as the one you built yourself.