Schroders Deli in Rome on Hwy 27 has a great burger.
Also, there is a little BBQ place at the intersection of Lawrenceville Hwy and Sugarloaf Parkway in Atlanta that has GREAT burgers. I can't remember the name of the place but they are worth a detour when you go to the Bass Pro. It is in a strip mall parking lot.
Years ago Pruietts over on Lake Weiss had a great burger, but I have heard that the quality of that food has fallen off over the years.