When adopting a false identity, the Master sometimes used an anagram. In 13th century England he went by Sir Gilles Estram, and on the starship Gallery he used Mr Seta. Each was an anagram of "Master". (TV: The King's Demons, AUDIO: Dust Breeding)
The Mimic's inability at original thought caused it to use anagrams. When it merged with Francis Pearson, it used the names Persona and Sperano, both anagrams of Pearson's last name. Even the name it became known by, Managra, was an anagram of "anagram". (PROSE: Managra)
Behind the scenes
Radio Times listings would often credit Anthony Ainley under a pseudonym to conceal his appearances as the Master before those episodes had aired. Usually, the names took the form of anagram of "Tony Ainley", such as "Neil Toynay" in Castrovalva or "Leon Ty Naiy" in Time-Flight, though the listing for The King's Demons listed him as "James Stoker", an anagram for "Master's joke".
Roy Tromelly was a pseudonym used to conceal the identity of actor Terry Molloy in Remembrance of the Daleks, so as not to spoil early that the Emperor Dalek was in fact Davros. It is an anagram of Molloy's name.
In the tradition of Ainley's pseudonyms, Mark Gatiss was credited as "Sam Kisgart", an anagram of his name, for his role as an alternate version of the Master, in both Sympathy for the Devil and The Emporium At The End.
Torchwood, an anagram of Doctor Who, was used at the beginning of the 2005 reboot to prevent interception of the first few episodes. The name was used as an in-joke in some series 1 scripts, and the Torchwood Institute was later a major plotpoint in the arc of the second series. Russell T Davies liked the name and eventually used it as the title of the first spinoff from the new series, Torchwood.
The Master when played by John Simm used the alias "Mister Saxon", an anagram for "Master No. Six" since Simm was the sixth actor to play the Master on the show. According to Russell T Davies this was unintentional.