Fish.
Supposedly I used to eat it without a fuss when I was little, but I can't remember ever liking it myself, so I must have been *very* little indeed.
It's a mix of both a taste and texture thing tho. It just feels... "wrong", in the lack of a better word.
The smell also causes me to feel mildly nauseous, both cooked and raw, so I hate walking by the fish aisle at grocery stores for that reason. Kills my appetite right there and then.
Cooked usually isn't that bad, unless it's boiled, at which point I also lose my appetite, but most other ways or preparation are ok.
Smoked fish, however, smells delicious, and I've rarely voluntarily eaten that on crispbread.