Squid or any animal that's equally as squishy. It's not the taste, that's fine (sometimes), it's the texture. The squishy, full-of-liquid texture that should be reserved for citrus fruit is terrifying for me when it involves something that was once moving around of its own free will.
I feel like I should mention a good friend of mine in this. She's the pickiest eater I've ever met. We tried to come up with a list of things she eats, and we got to 16, half of which were combinations of other things on that list. She survives primarily on a diet of potatoes, butter and bread. I'm dead serious. There was an article I read back in April that basically said, "You can live on nothing but potatoes, butter and bread" and my friends and I all thought, "Yeah, we know. Here's living proof of it."