We have hot dogs at home several times a month.
Our usual:
Her: mayo, relish (either dill or sweet)
Me: mustard, relish (prefer the dill)
On occasions we’ll add chopped onion and even less often, chili.
I think it may have been one of the Dirty Harry movies that shamed me away from ketchup. Before that I didn’t mind it if somebody else did the fixins.
I really like Chicago style, but it’s hard to find them in Oregon. Normally I go with mustard, relish and perhaps some diced onion and no fucking ketchup. Occasionally I like to smear on some crunchy peanut butter and a liberal dose of sriracha, but only if the dog is fried in a pan, not boiled. I know it sounds odd, but it’s very good.
Yeah, they’re just little peppers about the two inches long, and a similar heat level/flavor profile to serranos or possibly Tabasco peppers. If you ever find those jars of pickled Tabascos, that’s a reasonable substitute for sport peppers. I’ve also seen larger pickled peppers, serranos I believe, labeled as “sport peppers” as well. They are ubiquitous at Chicago area hot dog stands, where they are used on hot dogs, Polish sausages, and sometimes Italian beef (although giardiniera is the usual hot pepper accompaniment for beef.)
When I was down in Phoenix for Thanksgiving, I went to a place called Pittsburgh Willys to try the Twilly dog. What’s that? Hot dog in peanut butter, with bacon, served in a split Twinkie. Dare I say, it was surprisingly good. It’s never going to be my go-to hot dog, but it was worth trying and I’d definitely have it again.
I like them that way.
Or with mayonnaise.
Or with cheese sauce, pickle chips, and jalapeños.
Or with mustard and sauerkraut.
Or with catsup.
Or with catsup, mustard, and relish.
Or without a bun.
Or… Whatever. I just like hot dogs! 
While I usually eat them naked ( 
), with mayo, or with cheese and jalapeños, my favourite way is with chili, cheese, and raw onions.
Drag it through the garden. Chicago dog all the way.
If at home, I’ll usually do a ‘Red Hot’ with sauerkraut, mustard and perhaps ketchup.
Diced onions
Mustard
But limiting the discussion so we can’t discuss preparation? Why do you want to kill your own thread when it could just as easily be a 900 post flame war?
Sport peppers are definitely a Chicago thing. My GF, a transplanted New Yorker who thinks she knows hot dogs (and pizza, but that’s another story) *hates *sport peppers. I always stop her from having them “held” and eat them myself. Yum!
Meh. If I want a salad, I’ll have a salad.
By default: Mustard and fine chopped raw onion. But I’ve been known to enjoy some cheese, hot sauce, and/or chili on there.
A Chicago hot dog does not have that much stuff on it. The only extra vegetables you get beside the standard relish and onions is tomatoes and a pickle spear, and often enough people will eat the pickle spear separately, so really, all it is is a standard hot dog with some tomatoes on it. (And usually celery salt on a poppy seed bun.) Hot peppers are generally left off, in my experience, unless requested. (And, even so, plenty of places in Chicago don’t include tomatoes on their “everything on it” dog.)
Now, there are some weird places like Byron’s out there that will put lettuce, green pepper, and cucumbers on it, but they’re by far the exception. In fact, that’s the only place that comes to mind that has such salad-like ingredients.
I also heartily recommend jalapeno relish.
Mustard, chili, and slaw, in that order please.
Nobody has yet mentioned the single best thing to put on a hot dog: Cleveland’s own Bertman’s Ballpark Mustard. Yeah, other mustards are good, but that stuff is God’s gift to sausage. Back when I lived in Montana, I had to bring a couple bottles home with me whenever I visited.
But in general, I usually go for the works (which includes ketchup).
perfection
Oh, and since it hasn’t been mentioned yet…
boiling a hot dog is freaking nasty.
d&r
Also… what, really, defines a hot dog? Around here, one of the better local brands is from ex-NFL running back Earl Campbell and his line of sausages. Oscar Meyer is good for those rare times that I want to feel feel some nostalgia (it’s what I grew up with as a kid), but as a hot dog there are far better products out there.
Vienna All Beefs. Chicago Style on the condiments but I like mine grilled not boiled. Boiled tastes like balony. Poppy seed bun.
I like my hot dogs with melted cheese and ketchup. The best I’ve ever had are at the Hot Dog Shoppe in East Liverpool, Ohio.
Mustard, Onions, Tabasco.
Sometimes they hide the sport peppers in the Italian or Mexican sections of the supermarket. Other times they are in the regular condiment section.