Our ability to kill countless hours on YouTube is impressive and borderline unhealthy. There are literally millions of unknown singers who 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 seven celeb YouTube covers that are so great, they may even top the originals.