Wendy's for me, but when I used to live in El Paso, Whattaburger was the shit for 2am munchies. If you include not-so-fast food, I go with FatBurger. Or when I'm feeling dangerous, I go for White Castle.
A few months ago, I was at work and needed lunch, so I ran out to McDonalds, got me a 9pc McNuggets. I'm at my desk typing away, eyes glued to the screen, just grabbing nuggets to the side of me. I get to the last one and see this nasty purple hairy mold on it. Since I never took my eyes off the monitor, I have no idea how many of these had the mold when I ate them . . the sauce must have hid the texture and taste- GAH!!! AAAACK!!! Needless to say that was the last time I ate from that place.