I love things that are dedicated to a single purpose. Of course these things are essentially useless and from a technical or practical standpoint it would be better to use my phone, I place a high value in the experience of doing something, or even on very minor details such as the feeling of pushing a mechanic button vs pushing a "button" element in a digital UI on a touch screen.
The device that probably gets the most use currently is my iPod. I bought an iPod Mini (gen2) and I replaced the old hard drive with a high density compact flash card. The device originally had 4GB of storage, now it has 100+. I filled it up with a bunch of stuff I like and whenever I go to the dentist or ride my bike somewhere I like to bring it along and put it on shuffle. It's a great little device, I love it. I love how straightforward it is to use, and I love that I can just plug my headphones straight into it. My phone is supposed to be a better experience but it's always annoying to try and find something to listen to on Apple Music or Spotify, and I can't plug my headphones into my phone I would need Bluetooth and that's annoying because they you have another device that needs to be charged etc etc.
I also have a couple of portable cassette players. I actually like these more than the ipod simply for how analogue of an experience it is. I love inserting or flipping the tape, I love the big chunky mechanical buttons and the CHONK sound they make when you press them. I love the sound of the motor running, and I love watching the tape reels spin as the music plays. Of course my iPod is a far more convenient item and is technically better for that reason, but in terms of experience and the satisfaction that comes with using the devices, I love the cassette players so much more. There is a lot that could be said about this topic.
I started journaling a few years back, so I carry my journal with me sometimes but I usually just keep it somewhere around my desk. In the beginning I used a Hobonichi Techo so I bought a Mother (Earthbound) case for it, but I switched to a more free form of writing so I changed to a journal that's just empty graph paper without all of the extra features that the Hobonichi ones had (calendar pages, etc), but I'm still using the Mother (Earthbound) cover.
I started getting into drawing recently and have been learning the fundamentals. As a result, I recently started carrying a small sketchbook.
Words cannot express how much I love video games and so of course I have tons of dedicating gaming hardware. For portables though, I like to bring a Game Boy around sometimes. A few years back I picked up an Analogue Pocket and that has been wonderful.
This one might sound silly but I also carry a vintage pocket calculator sometimes. I hate using the calculator app on my phone, I want physical buttons and I usually need to reference data that's on the phone screen and it's annoying to switch back and forth so I wanted a physical calculator. But I don't like those cheapo modern ones that run on solar power because they're kind of shitty and I hate the squishy rubber buttons so I bought a chunky little Casio calculator from the 80s that runs on AA batteries. I love that thing.
As for cameras, I have a few. I have a digital (mirrorless) camera that I like a lot, but most of my love goes to my film cameras. My absolute favorite is my Canon AutoBoy 2, it's a point-and-shoot camera from the early 80s and I love how the photos turn out when taken with this camera. But more recently I have been shooting on a Canon Demi ee17. This one is also meant to be a sort of point-and-shoot camera, but it can be used fully manually. Being from an earlier era than the AutoBoy, this one doesn't require any batteries except for the light censor (which doesn't work, but that's fine because I got a small external one that sits on the cold shoe meant for housing a flash).