Harry Potter and the Half-Blood Prince
Professor: Transfiguration, Gryffindor Head of House, Deputy Headmistress
Affiliation: Order of the Phoenix
Professor McGonagall is the rather strict, stern, but, nonetheless caring head of Gryffindor House and Transfiguration teacher. She has been at Hogwarts for over 40 years, and when Dumbledore dies, she assumes the role of Deputy Headmistress. She is incredibly wise (she shares her name with Minerva, the Roman goddess of wisdom), and in Book 6 we see how good of an advisor she is. She gently nudges her charges in the right direction, advising them in their N.E.W.T. concentrations. She encourages Harry to pursue his path as an Auror, even in spite of a less than perfect O.W.L. result in Potions, and she encourages Neville to pursue Charms, even in spite of his grandmother's disapproval of the field. Professor McGonagall is a steadfast professor, who, unlike teachers such as Slughorn or Snape, cares solely about helping her students grow into the best wizards and witches possible.