All you need to make a beat is bang two sticks together. A child could do it (confidential to percussionists: we're not really serious. Please don't sue for libel). YouTube performers Wax and Herbal T took this idea to its logical conclusion and made a rap song using sounds from Herbal T's toddler son's playground session.
His voice hasn't dropped yet, but he's still dropping beats. Thirteen-year-old Chris Miles' submission tape for America's Got Talent has already impressed the denizen of the internet for his fast rapping ability, though his casual use of the word that rhymes with "tigga" raises some eyebrows.