Cheerios and Bugles (each separately). Nothing in either item should make them smell like death. But every flavor of either I've encountered always has. They're not even the same kind of grain.
I'll eat most ingredients in a wide variety of contexts. It's pretty rare that I'll find something that I don't like, and can't eventually find a way to like.
I'm not expecting them to be amazing, but them being substantially worse than bland and boring is still a surprise.