With the rise of YouTube, millions of unknown singers have proven their chops with impressive homages to their favorite artists. Some - Justin Bieber, anyone?! - have even scored record deals from their videos. What you may not know is that hidden amongst the sea of amateur renditions are some fantastic celebrity-done covers. From Usher revealing an indie rock side to Miley Cyrus showing off an impressive set of pipes, we've got 7 celeb YouTube covers that are so great, they may even top the originals.