Hard to say. To me, I believe Leonardo de Vinci. He was painter, sculptor, architect, musician, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist, and writer. He invented technologies that were way ahead of his time, and created some of the most famous works of art of all time. Albert Einstein, Steven Hawking, and other people like that also rank high, but I don't believe anyone has ever been so skilled as Vici in so many areas.