Offal of any type, from any animal. ExH loved liver & onions which I refused him to cook because of the smell. Also it tastes rank. He did try cooking it for me once and I threw up. My mum hates offal too. My daughter is vegetarian, so there's no love there either. But yeah, any "guts" or brains of any animal is gross.
I did try haggis in Edinburgh a few years back and with no disrespect to a great nation, I very much regretted it. Lesson, learnt.
My brother, my daughter & myself also have an aversion to mushrooms. It's unfortunate for DD when we go out for dinner & the only veggie option is mushroom-based.