I've had stinky tofu from a street vendor, which is both a fairly normal food and absolutely something that might cause a person to gag.
(As for the grossest thing I've eaten: one time, I found that beetles had infested my stash of buckwheat, so rather than letting them have it, I cooked it and skimmed them off when they floated to the top. I wouldn't do that again because I'm a vegetarian now...)