This was intended to be my contest entry, but I didn't have any time to work on it during the last few days of the contest or almost two weeks after. It's extremely small at 4.75" by 2.5" by 1.25", and can fit in a pocket. There wasn't any room for a speaker, though, so audio is only through a headphone jack and AV output jack on the bottom of it. It has an LED modded 2.5" screen (which is kind of dark, I think I made the resistance going to the LED's too high), tact switch controls (kind of stiff, but there wasn't room for rubber buttons), a switch for switching between built-in and cartridge games, and runs on four AAA's (not sure for how long, it's only been finished for about and hour).
Front (potentiometers at the top are for color and brightness, there is no volume control):
Top (sorry about the blurriness, you can kind of see the battery doors and the two switches for power and built-in/cartridge games):
Back (I actually used screws this time instead of tape or glue):
Bottom (the left jack is for AV output, the right one is for headphones):
Running built-in games list (with a cartridge next to it for size comparison. It's less than half the height of the cartridge.)
The weird ridge you see on the sides toward the back is a piece of 1/8" balsa wood I had to add because, just like in my original NESp, the case was not quite thick enough. I guess I didn't take the thickness of the wires into account. The rest of the case is high-impact polystyrene.