Asklemmy

Probably anything from this list of practices of eating live animals

Tomatoes

Will Smith eating spaghetti.

Balut - partially developed chicken or duck embryos. It's served a number of ways, but the one that turned my stomach was boiled in the shell and served like a soft-boiled egg. Watched my Filipino friend eat it. He scooped the whole thing into his mouth and when he bit down, the body cavity of the embryo ruptured, causing the entrails to pop out of his mouth. Then he slurped them back in like spaghetti. That's about when I refilled the beer pitcher with my puke.

Surströmming - fermented herring. Looks like rotten fish. Smells like rotten fish. Tastes like...well I don't know. All I can tell you is it was salty, but beyond that all I tasted was vomit. Watching a neophyte eating it will usually treat you to the sound of gagging, followed by vomiting. Maybe your own, since the smell is truly pervasive.

Some great stuff here, but I'll vote for natto. I enjoy it, but it is very gross to watch somebody eat, like seeing somebody eat a big bowl of the slimiest orange snot you've ever seen. Literally you can string it across a room.

It tastes like a mixture of cheese, hummus, and pungent soy sauce. It's definitely a different flavor, umami is the only way I can describe it.

Tuyo! My wife loves these. She'll make a big plate of them, then tear them apart with her bare hands, dipping them chunk by chunk into a small bowl of pickle brine. When she's done there's nothing left but a pile of eyeballs and lips on the plate.

Gagh

nothing more infuriating than people slurping liquids or noodles as loud as they can

I had a colleague that would bring frozen soups/stews, warm them just enough so that he could break through the ice, and he'd eat that. It was disgusting.

cherry tomatoes

In general, people eating are just not appetizing to watch.

Escargots, i.e. snails.

It's pretty slimy looking when people pull it out of the shell with a toothpick and eat it.

The flavour is not bad, but also not worth the experience, IMHO.

crab or lobster. they just look like massive spiders

In before ass.

Soup, hands down. Slurpers are the worst, but even not slurpers are disgusting.

Spaghetti if they're slurping it. Just because it has the convenience of existing in noodle form doesn't make it feel off to watch someone not use their silverware, even if I won't say anything about someone doing it in my presence.

seeing people eat tacos when they don't even know how to hold them properly

Everything eaten by Brendan in The Whale.

Anything where they loudly suck off their fingers afterwards. I know somebody that does, like, slow, sensual in-and-out, too.

Oysters definitely make the list.

sluuuuuurp