Lima Beans. I lived with my aunt and uncle when I was a teen and all they asked is that I eat one lima bean as I hadn't tried a lot of different foods. One single lima bean isn't a lot to ask--but it was huge for me. I hid it in my milk.
In retrospect, they would have saved themselves a lot of grief and me too if they had just let it go. I learned to eat all that stuff as an adult - ok not lima beans - but other foods I wouldn't eat as a kid.