If you think about it, airplane toilets. Small and efficient. They tend to have a clear design cue to know how to push open the door. The door lock also turns on the light, so it’s almost impossible to accidentally leave the door unlocked.
Frequenter suitcases. Only available in Japan, they have completely silent, user-replaceable wheels. The one I have is exactly the largest possible carryon size for most airlines.
Anker 45W usb-c GaN charger. It’s not much bigger than a standard iPhone charger. Overall a bit smaller since actually, since the power blades fold inside which is a nice touch. I just travelled for a month. I brought only this charger, one lightning cable and one usb-c cable. It was good enough, with a little bit of foresight to swap things out, to keep my all of my work and personal stuff charged (2 MacBooks, 2 iPhones, Nintendo switch, mouse and usb-c shaver). Made possible by the standardization of usb-c. It’s a bit of a nightmare for all of the various incompatibilities for data transfer and video but for charging it’s great!
GPS in cars, in Japan. They are usually slow and have terrible UIs. But, they usually give a picture perfect view of which lane to be in, even showing you the highway signs exactly as they appear in reality. And even 10+ years ago, a highway radio system broadcasts traffic conditions and (I think) highway toll information to the GPS units.
3M command strip hooks. Essential for home renters and have a clear indication of how to remove them.
Ski boots with a walk mode. At the lower end they let you walk easier but may be a bit less stiff. At the high end, they let you choose between touring mode and downhill mode, barely have a stiffness penalty and as a bonus let you walk easier. If you have a budget of under $800 don’t even try high end ones on because they are impossible to not buy. These are interesting to research too because it turns out there are only a handful of high end ski boot designers in the world and some of them are on the ski boot forums to answer your questions.
My biggest one is AirTags. They seem to be completely unadvertised recently, probably because when they first came out there was discussion about privacy. Like AirPods, you just open them and they sync and start working.
They are cheap for what they are, I got 8 of them and put one in every bag I use. I’m a forgetful person and have left many things behind over the years.
So far I’ve conveniently been able to find stuff I’ve left in another room, which is nice and once was alerted when I left my suitcase in one of the main stations in Paris. I got the alert that I left it behind well before I got on my train without it.
When I demo them to people, they are usually blown away when they realize they work anywhere there is an iPhone nearby. Not only near my iPhone.
I also put one in expensive shipped items for work. Has been great to be able to see where stuff is. It works reliable to things show up on the tarmac as soon as a cargo flight lands.