I think the most disgusting thin I've seen, but have not had the pleasure of trying, would have to be the KFC Double Down. Now...just think about it.
Two pieces of overflavored salty chicken with two pieces of cheese, and two strips of bacon. No bread, the chicken is the bread....not only can I imagine your hands becoming quite hot from holding the chicken, but you also get so much greasy on your hands, it's ridiculous.
Still, I haven't tried it so I can't say for sure. however, it sounds absolutely disgusting just from the description.