Chicago Restaurant Features "Most Metal" Burgers

Mayonaise,I agree...I've only had ketchup by mistake a few times over the last 10+ years. I just don't like ketchup.
 
I've never eaten mustard before. I'm not scared of it or anything, but now that I've waited so long, I don't know which kind of mustard is special enough to be my first.
 
In the Carolinas, they use mustard on their barbecued meats, instead of the tomato-based products the rest of the US uses.