It has to be the traditional hula dance. They have luaus at most major hotels, quite the tourist trap, but you have to see one and watch because their culture is very different than what I am used to.
Fondest memory: This is my favorite island, which has many waterfalls. I bought a book that was wrote by the locals, we hiked to the waterfall where 'Fantasy Island and Jurassic Park were filmed'. It was a restricted area, but we went anyway. Cool being at the top of that waterfall.
Fondest memory: Perfect view to Mauna Kea and its observatories. You just have to have luck to catch Waimea on a clear day.