I’ll go first.
When I was a kid my family had a TI-99/4A. The 99 series was Texas Instruments’ only real foray into the PC and video game market, and it failed to be competitive with Commodore, Atari, and Amiga. Most games were booted from cartridges.
My favorites were Hunt the Wumpus, a sort of early survival-horror with a turn-based grid system, and Alpiner, a mountain-climbing game with various hazards, kind of a reverse SkiFree. It also had the ability to read data from cassette tapes to load text-based games. The one I remember is Hammurabi, a sim/strategy game which I didn’t really get as a kid. Now that I’ve gotten into strategy games like Civilization and Romance of the Three Kingdoms it would be interesting to revisit.
I had a Casio FX-795P as a kid. Not really a game system, just a calculator with a one-line text display, but it had a BASIC interpreter built in so I made some games for it (a couple of text adventures and a side-view shooter.)