tl;dr: I'm going through a little nostalgia for (of all things) "MP3 players" (hereafter, digital audio player, or DAP).
As a category of devices, digital audio players only really existed for about 20 years, and they all but ceased to be popular consumer electronics in 2007, when the iPhone launched and popularized the concept of folding jukebox capabilities into phones (though many "feature" phones and PDAs had already been doing so for a few years). It took a little while for the devices to stop appearing on most store shelves, but nowadays the only ones worth using are traded on eBay and similar sites or forum groups.
My first MP3 players included my Palm Zire 71 (which required third-party software and an SD card) and a Craig device (which had 256 MB of internal flash storage, and no card slot); but my first "proper" DAP was a SanDisk Sansa c250 - gifted to me for my birthday in September 2007. I loved it - especially since it had 2 GB of built-in storage and a microSD slot for more, plus the fact that I could save my Zire's battery for other things - but after only three months with it, I found myself frustrated with the deeply-flawed shuffle feature and started seeking a fix for it.
And in December 2007, I found Rockbox.
Rockbox is an open-source firmware replacement for DAPs - including most non-Touch iPods - and it introduced me to a project and community through which I learned a LOT of Linux basics, some development fundamentals (I even wrote a section for the manual in LaTeX), and a few other things; I also made some very good friends.
Oh, and I turned my c250 into a powerhouse. Barring some issues with charging and USB transfers (which would be ironed out over time), installing Rockbox was an improvement in every way. It could play more file formats, it had a built-in file browser, customizable themes, simple utilities (like a calculator or stopwatch), games (like a Tetris clone!!), and way more settings than one could shake a stick at.
And yes, Rockbox's shuffle feature worked much better. I used it on every DAP I could since, and still do on the ones I still have.
Time has flown by since. When I got my first smartphone, eventually I started just using that instead of a dedicated MP3 player to listen to music, since it was more convenient to carry just the phone, more convenient to manage one portable music library, and more convenient to charge fewer devices. My current phone has no microSD slot, so right now I rely heavily on streaming/pre-downloading from Google Play Music, but that has its own share of frustrations - so sometimes, I break out the old phone, or even an old DAP, to listen to music instead.
Although the batteries in the DAPs have aged heavily and most of them no longer hold a significant charge. :(
Anyway, if you read all the way to this point, thanks for sticking with me. Feel free to share some of your memories of using MP3 players you may have!