The oldest functioning electronics I have that I still use today is a Pogoplug from 2010 that I purchased as new old stock in 2016, I'm using it as a non-critical nas every day when I roleplay as a devops engineer and ignore my actual degree.
The oldest functioning device that still works is a 12" Powerbook G4 from 2003, the battery still holds charge! I first started using OS X in 2006 when I installed it on my Shuttle XPC, bought a white Macbook a year later, couldn't reconcile how expensive it was so I sold it a year later and replaced it with a Mac mini and a 12" Powerbook G4 — then sold both to help pay for a gaming pc and ended up regretting it. I found a near mint one a few years for $75 and bought it immediately.
For me, the golden age of computing was in the sub 1GHz era, around 1999. Companies in the west started marketing "Internet Appliances" and to me, they were amazing machines.
These lightweight machines promised the Internet in a box, but delivered Internet jail.
www.pcmag.com
Cheap, slow, perfect for single-purpose machines. My favorite of these devices is the Webplayer, I've owned three or four over the years. For years, i used one as a winamp station.
I still have two that I hope to refurbish the form factor with modern components someday. Of everything I own, these are the most special to me.