Fugu

Puffer fish.
Usually eaten raw.
Usually eaten in Japan.
Apparently tastes like rubber band.

It's poisonous if you accidentally cut the sac that contains the poison while preparing the fish.
Many people have keeled over because of this.
So, if you're sure you want to try this, head on to Japan.

Osaka is known to have the most restaurants which serves fugu, but if you're in Tokyo, head on down to Usukifugu Yamada-ya in the suburb of Shibuya. It's a tiny restaurant, as with most great restaurants in Japan, cozy is the word and there are only 23 seats.