No. 9: Madonna

During her Twitter chat to promote ‘MDNA,’ Madge was asked about Bieber and said, “He’s awesome. I’m a huge fan. I love it when he raps.” She later addressed him directly when she wrote, “Come and join me on stage when I'm on tour when we are in the same city and congrats on your new single.” Sounds like there’s great duet potential here! Besides, nearly all of his collaborations so far have been with other dudes, so it’s time to see the Biebs give some lucky female a chance. Who better than the queen of pop music?