Excluding stuff like appliances like fridges and stoves and stuff like that, probably my Gameboy Color. I don't know if I use it daily, but I do play games on it quite a bit in my downtime. However I did replace the screen with a backlit IPS screen, and the case with the translucent green case, and I use a flashcart. Does it still count as old tech if the only original thing left is the motherboard and buttons? This feels like Gameboy version of the Theseus' paradox.
My daily driver is a Unibody Macbook Pro running Linux which I maxed the fuck out with 16 gigs of ram and a SSD, I supposed that's over 10 years old now and I use it every day.
I also have a set of Monsoon speakers like this hooked up to the line out on my TV:

I got them from the thrift store and I've only had them 2-3 years, so they're relatively new to me, but the company has been out of business since 2005, so they are at least 17-18 years old. I had to pick up a ground loop isolator, but they sound great.