Athina Onassis AONASSIS120406_1.jpgParis Hilton may be one-of-a-kind, but she's hardly the only billionaire heiress walking around these days - just ask Athina Onassis! Much like Paris, Athina, the sole heiress to Aristotle Onassis' shipping fortune, is forever finding herself in the limelight - these pictures, for instance, find her at an equestrian competition in Buenos Aires. But life's about more than shopping and schmoozing to this 21-year-old - believe it or not, she's already married for a year as of today!