So, I know it's been done before, and it isn't the most original idea ever, but... I built a working gameboy for my halloween costume last year. 
1. I always thought it would be funny to own a gigantic working gameboy
2. I thought it would be even better if I could wear it. 
That being the case, I built a fully working, to-scale version of a gameboy, which (for the most part) is accurate down to about 1/32" of an inch. I think, all told, it took about 70 hours to build, and probably cost about $400 just in wood, plexiglass, vinyl lettering, paint, weird tools and electronics and parts and things like that. 

It runs off of a Raspberry Pi with a PiCade X Hat hooked to a decased a computer monitor. The monitor is a widescreen monitor, with big sections of it covered by the body and the bezel... but because of that I can just let a red border show through and light up the "battery" LED area really nicely.  The controls work, the games are playable. The whole thing is rechargeable, and has about a 2 hour total run-time on a $90 pan-sized "battery" available from Walmart. It weighs probably over 50 lbs, and is a bear to get in and out of. It is not for the claustrophic as it's tight and inflexible 

 The shoulder pads are nearly non-existent and really uncomfortable. To be honest, it's a drag to wear, but it is fun nonetheless. 
It's 3/8 inch MDF over a frame of 1x1" pine boards. The controls are painted wood backed by plastic (to keep them from falling out), floating over the top of a control panel of push buttons which provide the keypress as well as the button bounce. 
The bezel is plexiglass with vinyl reverse lettering and stenciling for the lines and paint. The whole thing was painted with a sprayer and polished until it looks like plastic
The back has a slot for swappable "cartridges" in case I'm feeling extra. The battery compartment looks removable, but I left it solid to give the thing strength. 
Around the head area, the top is two breakaway magnetically attached wood panels. 
Very happy with the results. The one thing I learned from this experience: having people tap repeatedly on buttons placed in my midsection while staring feverishly at me is disturbing. It'd be a great costume to wear at some crazy adult party though  

Here's some pics: 
Body Front panel, early cuts

Front panel, early cut of d-pad area 

Body, unpainted 

Body back being routered

Back routering finished 

Back 
 Curved Bottom
Curved Bottom Bottom Curve Structure 

Bottom Curve Finished 

Bottom Curve Kerfed 
 D-Pad
D-Pad D-Pad being built 

D-Pad is mostly one solid piece routered 

D-Pad Nearly Done 

Controls being sprayed 

Controls being built 

Back of controls 
 Control Panel
Control Panel Control Panel 

Control Panel Installed 
 Bezel
Bezel Bezel Lettered

Bezel Steniled

Bezel Painted

Bezel Completed

Interior (TV) 
 Completed
Completed Completed with Gameboy for Scale 

Completed Side Angle 

Completed On 
