John Mayer

As suits his square-jawed, all-American good looks, Mayer pumps out easy classic rock for the freeway. It's authentic and soulful – even more so on his rootsy 2012 album 'Born and Raised' – and has won him a shedload of awards and mega sales across the Atlantic. In the UK, he's probably still better known for going out with Jennifer Aniston, Taylor Swift, Katy Perry, Jessica Simpson and Jennifer Love Hewitt. Though not all at the same time.