Growing up, I never owned a Game & Watch game, though my friends sure did. When I went to camp, the cool kids had them, and they'd hang out madly mashing buttons, trying to score more points in some food-flipping game, or the coveted pretty-good Donkey Kong game. But when I'd get to play them, most of the games were baffling -- either based on sports I didn't fully understand, or simply really hard to play due to the fast-moving (and hard to see) LCD action. Given my brief sessions with the weird LCD game thingies, I never became an expert.
Now, Pica Pic has put emulated versions of these LCD games online, for free. The controls are mapped to keyboard keys (and you can re-map them to other keys if you like). The games are still crazy-hard, but at least they're free! Go to Pica Pic to play. If you get a high score, you can even join the high score leaderboard on their site!
If you're not into the whole "playing the games" part, check out this Japanese TV ad for the multi-screen variants of Game & Watch games. Clearly, design inspiration for the later Nintendo DS:
(Via Kottke, specifically the excellent Sarah Pavis!)