Banana

Bananas were an Earth fruit. They were a good source of potassium. (TV: The Doctor Dances) They also contained vasoactive amines, which made some people (such as Toshiko Sato) vomit. (TV: Something Borrowed) Bananas were commonly associated with monkeys. (TV: Ghost Light)

The Doctor
The Second Doctor, objecting to Dastari's augmenting an Androgum's intelligence, said that if one gave a monkey control of its environment, it would fill the world with bananas. (TV: The Two Doctors)

The Fourth Doctor expressed a fondness for bananas, once stopping Bolog's fleet with one. (COMIC: Death to the Doctor!)

On Space Station Camera, the Sixth Doctor found a banana whilst searching his pockets for piece of wire. He gave the banana to Peri, who later started to eat it, but gave up when the sight of a dead Androgum made her feel sick. (TV: The Two Doctors)

The War Doctor used a molecular fruit bomb to transform the factories of Villengard in palm trees. (COMIC: The Whole Thing's Bananas)

The Ninth Doctor also expressed his fondness for bananas and briefly switched Jack's sonic blaster with one from Villengard to stop him from shooting at Jamie. (TV: The Doctor Dances) This incident caused Jack to joke that the Doctor had a "bananas only" policy, after the Doctor blew up his spare blaster. (COMIC: Weapons of Past Destruction) The Ninth Doctor also used a banana as a pretend weapon during an exploit within a Utopia window. (AUDIO: I Was Churchill's Double)

In his tenth incarnation, the Doctor still liked bananas. He claimed that while partying with Madame de Pompadour in 18th century France, he might have invented the banana daiquiri several centuries early. He also offered Rose the advice, "Always bring a banana to a party". (TV: The Girl in the Fireplace) He also liked banana milkshakes. (TV: Smith and Jones) When he tried to stop Sky Silvestry from copying him, one of the things he mentioned was a banana. (TV: Midnight) During a visit to Blackwood Falls, the Tenth Doctor ate two banana splits in quick succession. (PROSE: Forever Autumn) He described a "Banana Surprise". (PROSE: Martha in the Mirror) Once, when expecting to land on a sunny beach, he emerged from the TARDIS with an inflatable banana. (PROSE: Snowglobe 7) While searching through the the Doctor's coat, Rose found a banana. (PROSE: The Price of Paradise) In Twycross, the Doctor used bananas to lure some escaped monkeys into the TARDIS so he could return them to the zoo. (COMIC: Untitled)

When the TARDIS entered conceptual space, the Eleventh Doctor said "Imagine a banana - or anything curved - actually, don't, because it's not curved or like a banana. Forget the banana!" to Rory in an attempt to explain. (TV: Space) During a visit to ancient Egypt, he overturned a stall selling bananas while he and his companions were being chased. (COMIC: Assimilation²) In 1938 Berlin, he switched Melody Pond's gun with a banana to foil one of her attempts to kill him. (TV: Let's Kill Hitler)

Others
Reverend Ernest Matthews was given a banana by Josiah Samuel Smith just before Josiah turned him into an ape. (TV: Ghost Light)

Duncan Goode told Martha, "Don't judge a banana by its skin". (PROSE: Wishing Well)

Eugene Jones favoured banana milkshakes. (TV: Random Shoes)

After being defeated by the Tenth Doctor, Bob Kreesus slipped on a banana skin and fell over a cliff edge. (COMIC: Triskaidekaphobia)

At Twycross Zoo, Wanda taunted the monkeys there by holding a banana just out of their reach. (COMIC: Untitled)

When Ianto Jones was explaining automatic doors at the supermarket to Diane Holmes, John Ellis and Emma-Louise Cowell, the women were distracted when they spotted bananas. They were very excited to see so many on display, indicating bananas were difficult to come by in December 1953. (TV: Out of Time)

Jo Grant gave an Ogron prisoner a banana while en route to Earth in 2540. When the Ogron ate it without peeling it, Jo said "I think you're supposed to peel it first". (TV: Frontier in Space)