A kleptoplast is an organism that steals genes from other organisms, usually by eating them. Usually those stolen genes don't actually function, but not so in the case of the leafy green E. chlorotica sea slug. This little guy uses plant genes to generate its own photosynthesis factory - after eating its favorite kind of algae, the E. chlorotica can live entirely on solar power for up to a year.
New Scientist has a cool introduction to the life of solar slugs and their strange metabolism.
Solar Powered Slug article at New Scientist.