Earlier this year, reader Ilhan Ünal got started building his own Game Boy, which he only recently completed. It's... a little bigger than Nintendo's original version.
Named the Game Boy XXL, Ünal's handheld is more of a deskheld. It's running off a Raspberry Pi, with an old 19" computer monitor acting as the screen, and was built with laser-cut MDF (Medium-density fibreboard).
Here's some footage of Tetris being played on it:
And here's a NSFW shot of the XXL with its nude parts exposed:
You can read more about the XXL here.