As a chilean i completely 100% agree with the completo, it's one of the best ways to eat a hot dog. I also like the chili con carne hot dogs that americans make, half the time are meh, but when it's done right it's really tasty.
Personally i always use the same base: mashed avocado, diced tomatoes, mayo (home made or kraft), and the best sausage i can find. Usually premium. Then maybe sauerkraut, or different kinds of mustard, or some weird german sauces.