Max Thrun has written a detailed article on his hand-held gaming console based around the beaglebone black. It covers everything from custom PCBs, to a 3D printed prototype enclosure, to a final enclosure laser cut from delrin:
Older brother of the LaunchPad GamingPack, the BeagleBone GamingCape transforms your BeagleBone into a full fledged hand-held gaming console capable of playing all the classics such as NES, Gameboy, Sega GameGear, and even Doom. Just drop in 4 AAA batteries and you’ll be playing your favourite games
discretely at workin no time.