My sister likes to buy the ugliest cheap earrings she can find - the weirder the better.
When we were in our 20s & 30s, my brother traveled all over the planet for work. He always brought back souvenirs for the family and he’d pass them out at our parents house over dinner.
I discovered later that everyone thought there was discord between the two of us, since he never had anything for me. In reality he brought me home things he was embarrassed about; handmade pipes, roach clips, novelty rolling papers, strange porn, you know, brother stuff.
Pen or pencil, with some touristy thing on it, or a Christmas ornament. All of these are small and not too expensive. I still have several writing implements from a trip to Disneyland 20 years ago (the pen does not, of course, work any more).
Not specifically for travel but I like to keep the tickets from different events and use them as bookmarks. Then I use them,I get to remember the event
The Wife collects rocks and vintage postcards.
I like cheap tourist tee shirts, the one color printing with the place name and coordinates (or date established).
Oh, yeah, I have a friend who used to travel a lot. I always asked him to send/buy the tackiest postcard he could find at his destination. I think I still have them all somewhere.