Goblin Shark.

The goblin shark (Mitsukurina owstoni) is a rare species often called a "living fossil" -

This seems to me the strangest of all the sharks. It looks like some kind of prehistoric survivor, an experiment in shark design that doesn't seem to work. And yet, by definition, it does work. Triceratops,
the dinosaur with three horns, is long gone, as are Pteranodon and hundreds of other "impossible" animals. There is little that can be said about this mysterious shark, because so little is known about it. And yet, we have the most curious, incontrovertible fact of all: Mitsukurina lives.

Link | Recently, one was caught alive in Tokyo Bay but died after being put in an aquarium.