I usually lean towards Dijon Mustard on my grilled cheese.  Not sure how that started, but have been doing it for as long as I can remember. 

I always get “the look” from my wife but my grilled cheese needs ketchup.

I always get “the look” from my wife but my grilled cheese needs ketchup.

Well, looks like we have a winner!

Ketchup and mustard on the sandwich and dunked in Tomato Soup.  It was my birthday dinner as a kid.  Some think it is crazy, but don't knock till you tried it!