A Dallas institution, Keller's offers a hamburger dining experience like none other. The drive-in joint, in all its tattered glory, conjures up Happy Days memories with a grown-up twist. On a recent weekday evening, a line of cars formed in the drive-thru, where six-packs of Coors Light were the item du jour. Oh, and its hamburger is pretty good, too. Cooked to order, the modest patty comes with pickles, tomatoes and onions on a lightly grilled sesame seed bun. The price is old-fashioned, too: just $2.05. Add 20 cents for cheese.