The only "fast food" type I've seen mentioned here that I've eaten are Fuddruckers and Five Guys. It's Five Guys for me, definitely. I'm anxious to try In-N-Out when I head out west later this summer.
As far as restaurants go, I do enjoy Hard Times burgers as NMS alluded to.
That said, the deep fried "Heart Attack Burger" from Mother's in Fed Hill takes it for me... I mean just look at this description:
Beer battered burger stuffed with cheddar cheese, then deep fried and served with lettuce, tomatoes, onions, and chipotle mayo.
BTW, I seriously didn't feel all that great for about 20-25 minutse after eating one!
"You can't sit on a lead and run a few plays into the line and just kill the clock. You've got to throw the ball over the damn plate and give the other man his chance. That's why baseball is the greatest game of them all." ~ The Earl of Baltimore