Paris-based designer Laurent Milon makes rings decorated with iron filings shaped by magnetism, then galvanized with silver and nickel. He also made a cool video of the process that makes the emerging product look like a living, dancing animal.
Link via DudeCraft | Artist's Website | Video Link
(Not to mention snagging your clothes.)
On the other hand, it's the perfect gift for someone you're not fond of...
They would look cool as part of a costume.