There was discussion of fudge and Rice Krispie treats in the another thread, so I thought it'd be an interesting question.
At Walt Disney World - if I'm at the Pop Century, it's the cupcakes. At the MK, anything from Mrs. Potts. Epcot - the ice cream in France. Boardwalk - ice cream. DisneyQuest - chocolate cake (tons of frosting!) I'm not as tempted by fries, cheesy items, etc. I like chocolate, anything with lots of frosting, and ice cream. S'mores are really good at the campfire too, but I make better fudge at home.
Not that I'm eating all of those in a day. I'm heading out to Disney in a half hour, and I might have an ice cream (not everything from above). Otherwise, I'm bring fruit and some popcorn/pretzels in my backpack.
At Disneyland - my favorite items were the Chocodiles down the street (7-11), and walking across the street to McD's for ice cream. (much cheaper than in-park).
Oh - and I actually meant "food", not dessert. Some people are more into salty foods (or other items).