Hilo Hattie, Kauai
This is a close to a tourist trap that I can think of, price your souvenirs before you buy. Don't just buy from the first store, when there are a few shops to choose from, first look and then compare prices. We noticed many price variations with stores next door to each other. Sometimes you will buy one item and find the price was doubled upon visiting the next store. This is a typical thing that happens.
Unique Suggestions: Hilo Hattie usually had the best prices. See my shopping tip.