I can't really make up my mind about the worse thing I tasted. I've tasted a lot of bad things, and it's difficult to choose a winner.
I will say that I hate fish, or any aquatic animal. If it swims in the sea, I probably won't like it. Fish smell awful, too, and I just can't enjoy my food if someone else in the room is eating fish. It really makes me gag.
And for some reason, when I pop a fish in my mouth, I get this awful feeling like the fish might start moving of its own accord in my mouth, like it just suddenly came back to life when I started to eat it. It sounds really stupid on paper, but it's a horrible, horrible feeling, and it makes me really anxious and sick.
Now that I think about it, I can recall something that almost made me throw up on the floor. My family and I were having tea (or 'dinner') and we were having this Indian themed meal. On my plate was this brown thing. I thought it was some kind of chicken ball, and chewed it. Turns out it was this kind of goopy liquid protected by a thin, crusty shell. I gagged and spat it back out onto my plate, and rushed to rinse my mouth out. Euuugh.
Also, me and steaks don't really get along. I tend to choke a lot on steak.