True, Elvis loved his peanut butter & banana, but he liked his fried in butter. Probably also used the grease left over from his fried baloney sandwiches.

If we're allowing open-face sandwiches into the discussion, then I'd like to put forth my favorite cardiac-arrest-waiting-to-happen: Louisville's (Kentucky, USA) Hot Brown Sandwich. Toast on the bottom, thin slices of turkey, smother in a sauce made of butter, milk, Worcestershire sauce, and parmesean, top with more parmesean, broil till brown. Then drop two thick slabs of bacon on the top.