Changing up your hair is one of the easiest ways to reinvent your look, but what if you're more interested in cementing a signature style? Everyone from Becks to Bob Marley to Brian May has made a trademark barnet work for them. The trick? Find one classic crop that you can return to again and again, without looking like you’re caught in a time warp (sorry, Brian May). We’ve tracked down six haircuts that stand up to the fickle whims of time.