The hat that was made famous by John Lennon, He first wore the black Greek fisherman style hat during the first Beatles tour of America in 1964. The breton cap then became so associated with The Beatles singer that it gained the name "Lennon cap".
These days Facebook even has a John Lennon cap page that you can "Like" and Beady Eye singer Liam Gallaghers company Pretty Green sells the hats as the "Lennon cap", The legend lives on.