For myself I often buy a coffee cup of places I go to - usually just one of a whole trip, not every place on the trip. Something I use at home, not dust collecting, and I like having a range of coffee cups reminicsent of my travels.
Sometimes christmas ornaments from craft markets
Other than that, I sometimes buy little things for the grandkids - tshirts, little toys - eg in Budapest market I bought those little wooden nesting dolls
Sometimes I buy a tshirt for myself.