But ketchup is also ok.

tomatos add a real pop of sweetness, every hot dog i ever eat has mustard and tomato sauce

honestly all of these combos are oretty normal to me except maybe the sweet pie and cheese, but even then i think it could go kinda hard with the correct cheese

When I was younger I would have disagreed, but yes, hot dog and mustard is the amazing and has become my preferred condiment choice. Even better if you can throw some onions on it.