See, now this is the only correct answer, even though it is incomplete. Ketchup, good mustard and mayo on a burger, provided Frisch’s tartar sauce is unavailable.
Ketchup was only invented - by the potato growers of America - to disguise the taste of lousy fries. A good fry is never spoiled with a bit of ketchup. It exists as a thing of beauty in its own right.
Ketchup never, ever goes on a hot dog. Mustard, relish and diced onions. Spicy melted cheese is allowed. Chili dogs are allowed and encouraged. Ketchup is an infamia.