This Japanese video shows 32 metronomes set rocking on a wobbly surface. They begin in a state of chaos, and as they feed motion into the table, they begin to influence one another, until, 4 minutes later, they attain synchrony. It's quite remarkable (and a little sad for those of us with a nonconformist bent!).
メトロノーム同期 (32個) (Thanks, Fipi Lele!)