Leaf sheep (Costasiella kuroshimae) is a species of small sea slugs that can perform photosynthesis. Not many animals can do that. They are also adorable.

You should watch this youtube video of leaf sheep crawling about and / or read more about them on wikipedia, they are really fascinating!

Also check out Händeler, Grzymbowski, Krug, and Wägele (2009) “Functional chloroplasts in metazoan cells – a unique evolutionary strategy in animal life.”, they studied how long leaf sheep and other similar sea slugs retain their photosynthetic abilities after ingesting chloroplasts from algea.