Barbecue sauce
I know some of you will scorn me, but I agree — Miracle Whip. But I also think the world would be a sad place without horseradish sauce, too. 
Dijon mustard
Not weird to me, just a picky eater. I will eat salsa, small amounts of BBQ sauce and soy sauce. But no creamy dressings or anything that even resembles mayonnaise. No mustard or ketsup. It has been a problem for me sometimes when nasty condiments have already been applied, so I go without.
Mustard. Definitely mustard. And there are so many different kinds…
Deli mustard.
Others that are not “must have’s” but rather are treats are: truffle salt, balsamic glaze (for caprese salad) and blue cheese dressing.
Ranch.
I am a midwesterner through and through. Ranch was the only American thing I missed in Australia lol.
What’s the point of food if you can’t smother it in condiments? But if I could only have one, I guess it would be mayo. Also, please tell my H that salad dressings don’t count as condiments. I’ve tried but he doesn’t buy it.
mustard
you can do so very many things with Dijon mustard.
Hate ketchup and always have hated it.
Next would be Best Foods Mayonnaise.
A few nights ago I was sautéing mushrooms at D and SIL’s (he is the cook) and
was forced into being creative when he did not have worcheshire, tabasco or sherry.
I used butter, thyme and a dash of soy. They were good but not as good as usual.
Another vote for sweet-hot mustard. Love it!
Runners-up are hot sauce and ‘pick-a-pepper’ sauce. Is Worcestershire sauce a condiment?
Fry sauce. No question.
Hmmm. I will start by declaring that any condiment I can and do regularly make myself doesn’t count, including barbecue sauce, mayonnaise, aioli, chutneys, pickles, etc. I have made ketchup, but there’s something about good old Heinz that can’t be beat. I could make mustard, I suppose, but I haven’t. Similarly prepared horseradish.
This is tough!
I’m also going to declare that soy sauce, Chinese Chili Garlic sauce, and Hoi Sin sauce don’t count as condiments. Neither do vinegars and oils. The jury is out on Worcestershire.
Forget it, this is impossible! I guess I would have to say dijon mustard, if pressed.
@ski_racer What is fry sauce? Sounds intriguing.
I’d have to say ketchup, although I don’t use it as much as an adult as I did as a child. Need to add that I never put ketchup on eggs.
Salsa. It’s the zero-point blessing that makes Weight Watchers bearable.
Heinz ketchup. I love Sir Kensington’s mayo, so checkout clerk at our little hometown market recommended their ketchup. Tried it this summer and it didn’t do it for me. Back to Heinz and won’t stray again. I’m glad I won’t have to really pick just one as I love condiments and also having different choices for salad dressing.
Mustard! There are so many things you can do with it to complement different foods. It"s funny, I never would have predicted that would be my answer until I really thought about it.
A couple comments.
I say worchestershire sauce IS a condiment? Or is it an ingredient?
I’m surprised at how many say mayo. I rarely use it. What kinds of things besides a sandwich (BLT?) do you use it for?
@Consolation it’s a delicious mix of ketchup, mayo, and whatever else you feel like putting in there. I know some people add mustard, sriracha, barbecue sauce, relish, etc. Currently being marketed by Heinz as “mayochup”, although anyone who lives in Idaho, Utah, or Montana could tell you it’s called fry sauce. It’s also what a lot of burger places refer to as “secret sauce”.
Ketchup. And I confess that it is delicious with scrambled eggs. My husband shudders when I eat this combo. Otherwise, I do not eat condiments. Unless it’s bonding something together in a small amount (tuna or egg salad, for example), I really can’t stand mayo and the same goes for mustard. When I find myself with the choice of a pre-made sandwich with one of these condiments already on it, I elect to go without.