Let's talk about vintage handhelds, the types of devices where the games – usually only one – are built into the unit itself.
Pack Monster by Bandai was my childhood fav. I may have been 5 or 6 when I had it. Took me a while to find it because I had to jewgle "pac man hand held clone".
A friend of mine had the Mario Bros handheld. He left it at my house and never bothered to take it back with him, so I played the hell out of that, too.
OP edit: I didn't even see this thread >>15215156 . Looks like it's shit anyway.