I think Fatburger has a really good burger. It's a hand-formed patty and it's cooked after you order it. It's hard to find that in fast-food nowadays.
The topping are always good and fresh. I really like that they put both sweet relish AND dill pickles on their burgers. It's unique and it tastes good.
The steak fries are also good. Hard to find at a fast food place nowadays.
I always make sure to get Fatburger in at least once while I'm in Vegas.