Oldest machine I have is my sega megadrive 2, and some games for it. I never play it though as its the PAL machine and PAL games and they're much slower than their NTSC counterpart.
I also have my dreamcast but I don't play things on that anymore as the games don't look great on modern TV's without too much fiddling.
Oldest thing I used for years was my psp, upgraded that to a vita, now the oldest thing is use is my ps3 and I really don't use that much anymore. My lpatop, ps5, modded vita or modded 2ds is what I use these days.