Olives. I can't even pick them off something and eat it. Whatever the olive has touched is contaminated with olive-flavor.
And eggplant. I've tried & tried to like it, but it's always either fibrous or bitter. Actually, I had good eggplant once, in a Chinese restaurant in Nashville. The eggplant was all creamy & yummy...That's why I keep trying to eat it, but I've never found any like that again.