well, cheese, bacon, mayo and tomato are good, too.
also, you can put chicken nuggets in a hot dog bun.
tartar sauce is good, and of course real (aka dijon) mustard.
Ketchup is really a kid thing,kids love katchup on hot dogs because of the sweet taste.
I used put Ketchup on my hot dogs all the time, until I got to my late teens and early 20s, I started to put only Mustard,sauerkraut and Onions on my hot dogs. Every once in awhile i'll uses beer mustard, beer mustard have that sting that go all the way up to your head.
Well im english the "Hotdog" hasnt got the legendary status it seems to over the pond...For me i love ketchup, mustard and caramelized fried onions We dont even have dedicated Hotdog stores....just grubby side of the road carts !