Beard
A beard was a form of hair growth on one's face. They were often shortened to just thick upper lip hair known as a moustache.
The Master often wore one (TV: Terror of the Autons et al.) known as a goatee. (COMIC: The Judas Goatee) It led to the Fifth Doctor asking the Tenth if he "still had that rubbish beard". The Tenth Doctor replied that he had a wife instead. (TV: Time Crash) When the Twelfth Doctor reencountered the Master in his "Harold Saxon" incarnation, he had grown a beard. (TV: World Enough and Time)
Charles Dickens had one when he met the Ninth Doctor and Rose. (TV: The Unquiet Dead)
The Doctor first grew a beard in his fifth incarnation when he spent over a year stuck in Victorian London, as people thought he was too young to take seriously without it (AUDIO: The Haunting of Thomas Brewster, but he apparently shaved it off once he resumed his travels. While staying in the house on Henrietta Street in his eighth incarnation, the Doctor briefly grew a neat goatee beard, intended to test if he could change as well as the wider universe; he claimed to have worked out how to transform himself into a creature of pure light by adapting his self-biology, but estimated that it would take three thousand years of concentration, so growing a beard was easier. (PROSE: The Adventuress of Henrietta Street). He only kept the beard for a short time before he shaved it off. (PROSE: Mad Dogs and Englishmen, Hope). The incarnation known as the War Doctor grew a beard on a full-time basis. (TV: The Name of the Doctor, The Day of the Doctor) The Eleventh Doctor would grow a beard when held in captivity for significant periods of time. (TV: Day of the Moon, The Wedding of River Song) An alternate Twelfth Doctor wore one, too. (COMIC: Four Doctors)
In a Kantrofarri-induced shared dream, Santa Claus had a beard when he met the Twelfth Doctor. According to Wolf, he initially grew the beard as a disguise, but "people have picked up on it". (TV: Last Christmas) Indeed, even the Roboforms, who took the form of robot Santas, had beards. (TV: The Christmas Invasion, The Runaway Bride)
Owen Harper likened his partial resurrection to Jesus Christ "but without the beard". He immediately realised "shit, I'm never gonna have a beard" but denied wanting one. (TV: A Day in the Death)
Varun Singh had one grown due to the practice of Kesh in Sikhism. (TV: For Tonight We Might Die, The Coach with the Dragon Tattoo, Brave-ish Heart)