No. 7: ‘One Time’

A mid-tempo song with a bit of hip-hop bounce, ‘One Time’ was Bieber’s debut single, and produced his first music video, where he pursues a love interest at a house party. The clip -- featuring mentor Usher -- helped Bieber begin to win over the hearts of teen girls everywhere and served notice that the then 15-year-old was a talented new artist to watch.