One of my favorite retro game hacks: Dude took apart an old Atari 2600, figured out how the circuit board was setup and cut it up to fit into a little handheld unit. Built in the screen from a portable, handheld television set and wired in a four way button pad in place of the Atari joystick.
The resulting, portable Atari 2600 (plays the original cartridges):
The resulting, portable Atari 2600 (plays the original cartridges):
