Patty Melt?
I think that, among the fast food burgers in our area, Five Guys is among the better ones. But I read an article recently about somewhat off-menu options there, and saw that you can order a grilled cheese there and have them add a burger patty - effectively making a patty melt.
Haven't had a chance to try it yet, but wondered if anybody here has given it a whirl. Seems like it might be tasty!