Clinton Station Diner - Clinton, NJ
This cheeseburger is made with three pounds of beef and a hell of a lot of cheese on a delicious, buttery bun. If you can eat it in 45 minutes, it's free. There's no way on earth that is happening, but it's reasonably priced for the size, and it's very tasty.
The Atlas isn't their only cheeseburger of unusual size that you can order at the Clinton Station Diner. The biggest one on the menu is called Mt. Olympus. It's weighs 50 pounds total with 25 pounds of beef. The next largest is the Zeus, which is a 12 ½ pound cheeseburger with 7 pounds of beef. Next up is the Atlas, which is the one that I had (5 pounds total, 3 pounds of beef). There's also the Hercules (3 pounds total, 2 pounds of beef) and the Achilles (1 ½ pounds total, 1 pound of beef).
If you want to go in the other direction, they make something called Nano Bites, which they claim are the world's smallest burgers (to the best of their knowledge) at 0.4 oz.