RR and Fixin's Bar
I'm a big fan of Roy Rogers.
Yeah, I know, I know -- we do unique regional food on here, not chains, but -- well, there's really nothing regional per se with a hamburger. They're everywhere :-)
That said, I particularly like having the 'fixin's' bar at Roys. Pile on as much lettuce, tommato, pickles, onion etc as you like onto your own burger.
Any other chains do this?