Toppings
Mustard is probably the #1 topping for hot dogs. I doubt that any other topping even comes close. But that doesn't rule out many of the others like bar-b-q sauce, pizza sauce, chili, or catsup. Besides these sauces there is a multitude of other toppings that can be added to hot dogs like: relish, cheese, bacon, lettuce, tomatoes, onions, peppers, or pickles.
Chili Dog: Toasted bun, mustard, hot dog, chili, chopped onion, shredded cheese
Taco Dog: Toasted bun, hot dog, taco meat, lettuce, tomato, salsa
Chicago Dog: Toasted bun, hot dog, pickle, lettuce, tomato, celery salt