The MicrovisionThe world's first handheld gaming console. By Milton-Bradley. Released a full 10 years before the Game Boy in 1979. So the next time Nintendo tries to claim that they started "the handheld revolution", remember this guy.
The cartridges are actually the faceplates, which snap right on top of the unit. It has knob and button controls. And it has a black & white LCD screen. You may scoff, but this is pretty high-tech stuff for 1979. To put it into perspective, the Atari 2600 was the world's most popular game console.
I've got the original packaging included with it, even, which is pretty amazing considering I was even born yet (born in 1983). Unfortunately mine stopped working only weeks after purchasing it on eBay. These things are known to break-down easily being 30 years old and all. (Although they're usually known for screen-rot, with mine my buttons stopped responding). It's still a cool piece of history to have, especially since I have all the original packaging.
The only game I have is Block Buster, which is a Breakout clone (and was the original pack-in game). There were other games released for it like a Star Trek game, a bowling game, a pinball game, a space-ship shooter, and others.