No. 1: Julia Nunes, ‘Baby (Where Did Our Love Go)’

A quirky mashup of Bieber's 'Baby' with the Supremes' timeless Motown standard 'Where Did Our Love Go,' YouTube star Julia Nunes offers a refreshing take on both tracks that gives us a major appreciation for each song. The perky blonde multi-instrumentalist pulls out pretty much every trick in the book (ukelele? Check. Funny hats? Check. Oversized drum? Check!), but her likably husky vocals and sweet style are anything but gimmicky, making this our No. 1 Justin Bieber cover on YouTube.