Heavily Modified Sega Game Gear
This was a super fun project which isn't quite completed, but close!
Basically, this is the original Game Gear shell and main board with a new display (BennVenn IPS LCD), Clean Juice power board (featuring USB-C charging and internal rechargeable batteries), and sound board (with crisper audio and all-new components). The main board has been recapped. Also included are seven games: Surf Ninjas, Ecco the Dolphin, Mortal Kombat, The Lion King, Primal Rage, Sonic the Hedgehog 2, and Wonder Boy.
Now, the bad: I would not consider this complete. The shell in particular still needs some cleaning, and the lens is pretty badly scratched. Some games you may need to power cycle to start (once started, the games run fine). The Lion King cartridge is probably bad, I can't get that one to work. I would not suggest picking this up unless you're prepared to tinker.
Asking $160 shipped.