I loved my TI-83 back in the day. Ion Shell + zTetris + Link Cable was a blast back in High School. Solytare was also solid.

Those were good times.

I still play these games every once in a while, albeit on an emulator these days. WabbIT Emu is pretty nice and has some very nicely rendered skins that replicate these calculators perfectly. I also still use the emulator for the occasional calculation just because I'm so familiar with how it works.