Casio Hippo Mouth Game!
Bookmarked for sentimental reasons.
I have one of my own. The game plot - a little mouse jumps in and out of the hippo's mouth to brush its teeth while trying not to get munched and avoiding rocks/coconuts being chucked by monkeys.
My brother had one called Canoe Slalom (I think) and Caroline's was a circus themed game. Were they as good as a Game & Watch? They might not have had the street cred but they certainly kept us amused on long car trips.