Puffer Fish

Pufferfish are generally believed to be the second most poisonous vertebrates in the world, after the golden poison frog. Certain internal organs, such as liver, and sometimes the skin, are highly toxic to most animals when eaten; nevertheless, the meat of some species is considered a delicacy in Japan when prepared by chefs who know which part is safe to eat and in what quantity.

http://en.wikipedia.org/wiki/Tetraodontidae