Donkey Kong II (Game & Watch, with dual-screens)
I haven't played it in a few years, I'd need to just get replacement batteries,
but that's a game I remember having to and feeling like I can go on and on. 
They're not really play through-able (G&W) however they're kind of like that,
accidently playing away through an old game!
I'd love to be able to play more Game & Watch games! I remember finding an
actual watch-sized online and was stoked even just to hear about it!
They are simply (addictive) fun!
