Labor Day weekend, I visited the fine establishment that is Southside 815 in Alexandria, Virginia. I only ate 1/2 a burger that day, but it was juicy and filled with great grill flavor. The bun did not overwhelm the burger, and it was accompanied by a great pint of Guiness.
While not a burger, the peach pound cake served with vanilla ice cream was sublime.
You should go there and try their food. Just don't forget to give very large tips to the bartender.