Magnapinna squids are one of the deep-sea more ethereal creatures.

Little is known of these squid as very few have ever been captured, although over the last decade with the increased usage of remotely operated vehicles (ROV) and submersibles more and more video is emerging of them.

They are unusual in both that the fins are up to 90% of the length of the body, i.e. the mantle, and the ridiculously long length of the arms.

Via Deep Sea News, with more info on them available on Wikipedia.