I had a Sega GameGear as a kid. Yeah it was a Sega system, which Sega was major back then, but the GameGear was nothing compared to the Gameboy. Very cool system, in that it had a full color screen and was backlit.

Now that was at the expense of being heavy as all hell and a monster eater of AA batteries. 6 of them at at time!

I think that was basically the only non-major system I had.