Some snacks are available everywhere, typically these are ice cream snacks from Nestle, Rice Krispie Treats, and Resort Branded Candy.
IMHO, these are special snacks:
Yes, Dole Whips are fantastic. Aloha Isle in Adventureland.
If you can make it to AKL, Zebra Domes are still good. (They used to be great!) You can get them in the Mara food court.
In Epcot's Japan Pavillion, Kaki Gori offers some really good shaved ice.
In Epcot's France pavillion, I love the creme brulee. They have many, many other good french treats.
Starring Roles in DHS has some wonderful looking sweets. I cannot remember the name of what I ate there, but it was good.