Scarlet Fever

"Scarlet" as a name has always invoked an air of passion and sensuality. Usually a female-oriented trope, the name "Scarlet" (sometimes with two T's) often denotes a woman with a fiery, indomitable personality and complicated morality. If she's a hero, she'll be on the aggressive side. If she's a villain, she's almost never straightforwardly evil. As one can expect, she is often a Lady in Red and/or a Fiery Redhead, especially if "Scarlet" is actually a nickname or codename.

While male examples exist (Captain Scarlet and The Scarlet Pimpernel come to mind), they usually have a much different feel, playing up the boldness of the color red rather than any direct sexualization.

Anime and Manga

 * Erza Scarlet from Fairy Tail.
 * Freezing's Dr. Scarlet Ohara, who's willing to do anything to save the world including.

Comic Books

 * The Scarlet Witch from Marvel Comics.

Literature

 * Scarlett O'Hara from Gone with the Wind, possibly the Trope Codifier.
 * Miss Scarlet from Perry Moore's Hero, a superheroine with fire powers to match her temper.
 * While not the name of a person, The Scarlet Letter invoked this trope in its title as far back as 1850.

Music

 * Scarlet's Walk is an album by Tori Amos where the character, Scarlet, travels the U.S. post 9/11.

Tabletop Games

 * The sultry Miss Scarlet from Clue.
 * The Scarlet Empress, one of the primary villains in Exalted.

Video Games

 * The vampires Remilia and Flandre Scarlet from the sixth Touhou game, Embodiment of Scarlet Devil
 * Final Fantasy VII's Scarlet, who is a mid-level villainess, a Corrupt Corporate Executive and a Lady in Red.

Western Animation

 * Scarlett, the most well-known female hero from G.I. Joe. Her backstory is an homage to Gone with the Wind, as her birth name is Shanna O'Hara and she's from Atlanta.
 * On The Critic, Jay's boss Duke meets Alice's Southern Belle sister Miranda at a costume ball and is instantly smitten with her, nicknaming her Scarlet.

Real Life

 * Famed sex worker advocate Carol Leigh, aka "Scarlot Harlot"