The one I had as a child at The Land in Epcot was comprised of a cone of bread (like a cross between a pita and an ice cream cone), sliced roast beef, and a cheddar cheese sauce.
Because there was only one open end, it was less messy to hold than a flatbread/wrap, but because the top had to be so wide to accomodate the filling, eating it was much messier (the first few bites -like eating an ice cream cone- had to be all beef/cheese, which often resulted in cheese-and-grease-covered noses.)
Disney's Handwich: The sandwich of the future!
I wish we had more unique fast-food offerings, however looking back, I think I would be less apt to order it as an adult than I was as a child (I really hate being messy when I eat... really...)