Macropinna macrostoma (common name "barreleyes") can rotate its eyes to a vertical position; because its head is transparent, it can then see predators or prey above itself without moving its body!
Two net-caught individuals contained fragments of jellyfish, which must have been their last meal. Such a potentially painful dinner requires incredible stealth, so it's now thought that barreleyes carefully maneuvers its body near such stinging organisms, keeping its "eyes on the prize," as the researchers said, throughout the entire hunt. Its tiny mouth then picks at the victim while a transparent shield protects the fish's eyes.
http://blogs.discovery.com/news_animal/2009/02/see-a-fish-with-a-transparent-head.html - via reddit(image credit: Monterey Bay Aquarium Research Institute)