Poi.
I've ate stuff with tentacles, I've had frog, turtle, even snake. I've eaten vegetables that were pickled that shouldn't have been and fruits done in ways that made no sense to anybody. I've had spicy food so hot I couldn't breathe then and nearly cried the next morning, and things so sweet they glued my teeth together for five minutes. A friend's wife made spaghetti sauce that was a crime against the history of Italian Food, and I've had pound cake from a bake sale that would be an honorable mention on the Darwin Award site if they covered food. I've worked in kitchens that regularly cooked premade hamburgers that smelled like gym shoes, and had fish patties come out of a fryer and you had to let them set for awhile before you served them because inside the breading the 'fish' part would be liquid until it cooled (and no, it did not taste like any known species of fish).
I have one answer to the question of what was the worst thing I've ever eaten.
Poi.