One of these #OldDevices I had ca. 2004 was a Creative Jukebox 3. It was an awesome mp3 player that looked like a discman, with 20GB of storage (❗) and such features as changing playback speed. It was super helpful when learning songs by ear on the guitar to slow things down. Now I struggle to find an app on F-Droid to do the same, and it took me a while to find out that VLC exists on Android and can do that.
I also miss the tactile feedback of physical buttons. Awesome product.

The only drawback I can think of was that the Jukebox was pretty heavy. Not the kind of thing you’d want attached to your body when going for a run. Hence me adding a Samsung YP-U3 to my collection of #OldDevices in 2008. Only 1GB this time, but in a very convenient USB stick form factor with a removable clip to attach it to your clothes or backpack strap.
That one too must be hidden somewhere.