Homemade souse or head cheese. It depends on where you live which it is called. To me it looks like, smells like and tastes like congealed vomit. Blood boudin isn't a favorite either but that is because it tastes like liver. Blood pie or blood pudding ain't going down either. Liver in general is pretty disgusting tasting too but that is just a personal preference thing. That makes it bad because I'll eat anything.
When I was growing up in Micronesia there were a couple of times where we were invited to a meal featuring roast dog. Back in the day, dogs weren't pets; now I'd just as soon eat a person as a dog....
Number 1 would probably be menudo, but broccoli, cauliflower, lentils and Lima beans are all a pretty close second. Take your pick. None of them will even stay down.
I'd have to say lizard. When my son was about 10 or 11, I made him and a friend of his camp out all night on some rocks by a creek. The next day, I told him to catch something to eat. He caught a lizard, made a fire, cooked it then we all tucked in. Not the nicest. Needless to say, his friend never came over for another "sleepover".