I would have to say Dairy Queen. I worked there when I was 17.
You would be amazed at how upset people get over some friking Ice Cream. I had a lady seriously get out of her car and demand to see my manager because the whip cream on her sundae wasn't 'Creamy Enough'.
Sometimes, I'm a bit 'flip' or as I like to say quick witted...lol
So I told her "Maam, whip cream is only about 1.50 at any fine retailer, since our version doesn't quite suit your fancy." She was TOO heated.
I submitted my resignation after a week of employment....lol