A sense of style — in other words, bringing a creative eye to what you wear. What's even better is that you don't need lots of cash to have it, either — just the ability to take what you have and put it together in a thoughtful and interesting way, or by adding an unexpected detail, such as the green gloves in the classic evening ensemble above.
1953 Vogue photograph of Suzy Parker by John Rawlings, via myvintagevogue on Flickr.