Not sure if you are looking for a snack or a dessert - but my daughters' favorite was the Kona Kones at Kona Cafe.
As a side note, I mentioned jokingly to the waitress that we were going to sacrifice our desserts and trade with the girls, for their desserts. She said that since we were on the deluxe dining plan they could get Kona Kones and we could also get desserts off the regular menu, we didn't have to trade. Not sure if it was standard practice or just that server, that's the only adult dessert they really wanted - but they did enjoy those Kones!