Bun fright One of my pet peeves when eating a hotdog is when the sausage is shorter than the bun, or vice versa. An empty bun is just bread, while a sausage without the bun is just a sausage - it's only when they're combined that they make a hotdog.
Another point that I feel very strongly about with hotdogs is that the sausage has to be made with real casings: the artificial ones lack the crisp "snap" you get from casings made with intestines.
Other than that, though, I am pretty open to the many different styles of hotdogs. In Los Angeles, I have eaten Oki dogs (two pastrami-encased hotdogs with chilli, wrapped in a flour tortilla, rather than a bun). When I was studying at UC Berkeley, we often took time out from cramming for exams to eat hot-link and kielbasa hotdogs at Top Dog. I even like the boiled "dirty water" hotdogs sold from carts in New York, which I learned to eat properly, with "the works" - onions, relish and mustard; never, ever ketchup!
If I had to pick a favourite, it would be a juicy grilled pork or beef hotdog in a tender bun, topped with all-meat chilli (no beans, please!), some grated cheddar cheese and chopped raw onion.
The one drawback that prevents hotdogs from being the perfect, transportable snack is that if it's a good one, it's rather messy. Only children eat "naked" hotdogs. For the rest of us, a hotdog's toppings are what take it from the good to the sublime.