Kopi Luwak is also known as Civet Coffee.  It is quite literally made of coffee beans in Indonesia that have passed through the digestive tract of a Civet.  Um, yes.  Pooped out coffee beans.

Apparently, besides being quite rare, they are also quite tasty when brewed into coffee.  A pound of Civet coffee beans is approximately $227.  And you thought Starbucks was expensive!

The New York Times has a pretty amusing and educational article on the subject. Wikipedia does not disappoint: there is an extensive article on the subject with links to other sources.