"American Boy" - Estelle featuring Kanye West.
For me, one of the most enduring chart hits of the year. Featuring Kanye West - I know that was quite a common thing a couple of years ago - every record that was released seemed to be 'Featuring Kanye West' but his rapping on this one just makes the song extra special, and it's quite funny too.
Estelle hasn't really had much commercial success since, possibly because this song will always cast a big shadow over anything else that she does. This song was a breath of fresh air for many of us who were becoming bored by the dull formula r'n'b that ruled the charts this year: just a great crossover record.