Because of my diet, I eat veggie dogs (but not tofu dogs), and I add ketchup, (German or baseball, but not Dijon) mustard, sour pickle relish (never sweet), and onions. I have sometimes added chilli peppers, but since I am not very partial to piquant foods, quantities have been small. I have tried organic hot dogs, though, and they are very good, but unfortunately also a luxury for me.
On the whole, I prefer bratwursts, frankfurters, and other kinds of European (and especially German) wieners to hot dogs. To these I usually add German mustard, onions, and sauerkraut.