Hat

A hat was an article of clothing worn on the top of the head.

The Doctor's hats
Throughout the majority of his lifetimes, the Doctor wore a hat on a regular or semi-regular basis. Only a minority of incarnations — that is, the Sixth, Eighth, Ninth and Tenth Doctors — never showed a particular interest in hats.

The First Doctor
The First Doctor's usual hat of choice was a karakul, a warm, triangular hat. It was this hat he was wearing when he met Barbara Wright and Ian Chesterton, as well as during his first adventure with Ben Jackson and Polly Wright. (DW: An Unearthly Child, The War Machines) However, he was also known to possess a kind of Panama hat, which he wore in hotter climes. For instance, he was seen to don an apparently white Panama when he was on the hunt for the Daleks' taranium in Egypt. (DW: "Escape Switch")

This incarnation was not averse to occasionally playing dress-up. When in Revolutionary France, he obtained period-appropriate wardrobe. Because the costume was that of a regional official, his hat was particularly elaborate, bearing a strong resemblance to an early 18th century French army officer's hat. (DW: "A Change of Identity")

Second Doctor
Second Doctor wore a stovepipe hat early in his incarnation. The Eleventh Doctor was fond of a variety of hats. While in the National Museum, the Eleventh Doctor found a fez which he became very fond of. The fez was later removed by Amy Pond and destroyed by River Song. He sought another fez after this. (DW: The Big Bang, DW: The Impossible Astronaut)

The Eleventh Doctor acquired a Stetson hat from Craig Owens.(DW: Closing Time) He was last seen wearing it inside the Teselecta. (DW: The Wedding of River Song).

The Eleventh Doctor owned a top hat, which he wore at Amy and Rory's wedding, after having been poisoned by River (DW: Let's Kill Hitler) and again to conceal a device that allowed him to lure the Squall back into their dimension of origin (NSA: Paradox Lost).