I can't tell you about the abdominal pain I've had after visits to many of these places including Five Guys. Still, not a thread about nutrition. This remains my favorite.
Mine is Fatburger. I wanted to vote for Long John Silvers just because it's there. I haven't had it in well over a decade though.
Lately I've been either getting the chop house cheddar burger or the patty melt and adding grilled jalapenos plus an egg at Whataburger.
Are sandwhich shops considered fast food? If so then my vote would go to Which Which. If not, then I'd probably go with Arby's or Whataburger. But I rarely go to fast food places anymore. I don't know if I'd consider Taco C or Beck's fast food. Definitely not Beck's since their food is kind of expensive (but damn good).
I totally forgot about Beck's since I'm not in Houston, they are probably my #1 I consider anything fast food if they have a drive thru
Popeye's is my favorite. I'm going to throw a dark horse candidate out there though...Raisin Cane's. All they serve is chicken fingers but its so good especially the sauce. We had one that was a block away from my apartment in college that stayed open till 3 AM on the weekends.