I'm a Chicagoan, so I like all-beef dogs the best, but I'm not one of those no-ketchup purists (just as I don't get into the thin-vs-thick pizza crust debates; like Andrew Zimmern, my attitude is, if it tastes good, eat it!)
I like some but not all of the Chicago-style toppings. Specifically: mustard, grilled onions, pickle spear, celery seed, and yes, ketchup.
All the above great on polish sausage too.