Vera's Burger Shack if we're allowed to talk about local chains.
I don't think that counts as fast food, though. Fast food should be ubiquitous and have thousands of locations. Limit this thread to BK, Wendy's, McDix, Jack in the Box, A&W, Dairy Queen, Hardy's, Carl's Jr., and maybe one or two I'm forgetting and be specific, otherwise this just turns into another "best burger ever" thread. I enjoy the angry whopper and the flamethrower but I don't eat much fast food.