Depends on how you define Fast Food. If its simply a place with a drive thru it would be:
Mo bettahs
Cafe Rio
In N Out
Panda Express
Taco Bell
Apollo Burger
Taco Time
Jimmy Johns
Arbys
Raising Canes
If Nielsen's Frozen Custard counts it is #1 by a long shot, amazing burger and best custard/ice cream around.