Down With Love - Renee Zellweger's character stops being a wimpy woman and dyes her hair red to show it.
Charlene, played by Amy Adams in The Fighter, who delivers the immortal line "Don't call me a skank. I'll rip that nasty hair right outta your fuckin' head."
Diamonds Are Forever. When James Bond first meets Tiffany Case, she's outspoken, quite rude to him, and has a bit of a temper. She changed wigs (from blonde to brunette), then appeared as a redhead.
James Bond: I don't care much for redheads. Terrible tempers. But somehow it seems to suit you. Tiffany: It's my own.
The Ur-Fiery redhead, Mary-Kate Dannaher in John Ford's The Quiet Man. As another character puts it, "That red hair is no lie!" She tries to slug out John Wayne himself! Maureen O'Hara's finest Fiery Redhead hour.
Bortai, the redheaded Tartar princess played by Susan Hayward in the John Wayne flop The Conqueror.
Ginny Weasley from Harry Potter is a double subversion as she is usually soft spoken but:
Harry: Okay, so this morning I'm going to be putting you all though a few drills, just to set things straight... [Everybody keeps talking] Harry: Quiet, please! [Nobody listens to him] Ginny: SHUT IT! [Silence] Harry: ...thanks.
Ann Sheridan in several movies from the late 1930s/early 1940s.
Shapeshifter Mystique, usually doing infiltration and other covert ops in the X-Men comics, is more like the mutant version of the Angry Black Man in the movies. She's red-headed in both incarnations.
Shannon of Far and Away fits this easily.
Joseph: I warn you. That redhead has a bite that stings.
Henriette de Nevers is an understated but still adventurous redhead in the film version of La Reine Margot.
Gimli of Lord of the Rings has red hair with a matching beard as well as being quick-tempered. Well, the temper part is kinda obvious because he is a Dwarf. Same goes for his father Glóin in The Hobbit.
Spirited Ashley in Junebug is a midler and realistic version of this.
