Sienna Miller "has that cool Brit-girl sense of style and mixes designer with vintage," says Kaufman of the budding fashion icon (left, in London; right, at a polo event in Berkshire). "Somehow she puts it all together and makes it work." The handbag company Kooba even named the highly popular Sienna bag after her. But her biggest fashion feat? "She single-handedly brought back the denim vest," says Kaufman.