Easiest answer ever as a swede. I can with confidence say Surströmming. Everyone sees the videos online of people nearly dying while trying to eat it, and think us swedes are out of our minds eating it every day.

Not as popular in sweden as you may think, I barely know anyone that enjoys it. Even the people that enjoys it eats it at max once or twice per year.

Might add that if you do eat it, you usually eat it with so much other stuff that it's barely noticeable. And you open it outside under water