Mushrooms. When I was younger I just knew I hated them, then as I got older I realized it was because after I had more than a mouthful of them my throat started burning. I figured it was an allergy and that was that... then I fell in love with a woman whose third favorite food is mushrooms. She spent years trying to find a way to get me to appreciate mushrooms, and not a casual effort I should add. First we figured I was fine with Enoki mushrooms (the little beansprout-like ones you get in Miso soup sometimes), then it was Oyster mushrooms which are pretty damn versatile, if low on flavor. Started incorporating those into my cooking, and for years that was the extent of it until one day I had something with white mushrooms in it and realized the damndest thing: my throat wasn't burning. I'm not sure how or why, but whatever problem I had with mushrooms had gone away. Now I have mushrooms almost every day, usually as part of my breakfast.
I thought this was going to go a very different direction. Mushrooms are good though, in both contexts. I also used to hate them as a kid but my parents would always eat them. Over time I learned to love them and now I always have mushrooms on hand. They go with every meal.
The other type is also good to have on hand, but does not go as well with meals in my opinion.
Funnily enough the one time I had the other kind of mushrooms I was expecting them to taste awful based on all the warnings and my own issues with mushrooms. Turns out I don't mind the flavor that much.