What's the best system of magic in any fantasy world?

Every fantasy book or movie treats magic differently. Sometimes, magic is a totally unknowable force, and controlling it is like steering the ocean. Sometimes, magic is logical, and you just need to know the rules. But which fantasy story has the absolute best system of magic of all time?

Please include a picture of your favorite magician or magical world, with the most well-thought-out or coolest version of magic. Thanks!

Top image: Tales from Earthsea, mostly chosen to represent Ursula K. Le Guin's Earthsea books.