Gryffindor emphasises the traits of courage as well as "daring, nerve, and chivalry," and thus its members are generally regarded as brave, though sometimes to the point of recklessness.
Notably, Gryffindor house contributed many members to Dumbledore's Army and the Order of the Phoenix. According to Phineas Nigellus Black, members of other houses, particularly Slytherin, sometimes feel that Gryffindors engage in "pointless heroics." Another Slytherin, Severus Snape, considered many Gryffindors to be self-righteous and arrogant, with no regard for rules.
However, this may be taken with a grain of salt, as Gryffindors and Slytherins have shared a fierce house rivalry since their founders, Godric Gryffindor and Salazar Slytherin, respectively, had a severe falling out over Slytherin's emphasis on blood purity.
Head of House: Minerva McGonagall
Ghost: Sir Nicolas de Mimsy-Porpington