Mullumbimby, NSW, Australia. Proper small town vibes, but features a small park, an awesome local pub with a great and affordable steak, a wonderful Indian food restaurant, a spa, etc. But also sufficiently close to former hippie and modern day hipster/tourist hotspot Byron Bay as well as beaches both north and south (including Brunswick Heads and the awesome drum circles happening there every Sunday)

Suure-Jaani, Estonia. Probably mostly because it's my hometown, but it's also very beautiful (in the summer) and it's close enough to places like the Soomaa bog (one of the most peaceful places on planet Earth IMO), Viljandi (hosting some great cultural events) and Tartu (the student capital of Estonia).

Kampot, Cambodia. Civilized / built up enough to have a good time and enjoy life, while still being quite rural and uninterrupted by large hordes of tourists. Great place to ease yourself into the Khmer culture.

I don't have a proper bucket list of small towns to visit, but I generally do prefer them over big cities. In New Zealand, where I'm at right now, Kerikeri seems like a pretty cool place (haven't stayed in town though) and I've heard good things about Raglan (supposedly the New Zealand equivalent to Byron Bay)