Duel of Seduction

A Sister Trope to Ladykiller in Love, this is what happens when The Casanova and the Femme Fatale (Or some similar character archetypes) are both trying to seduce each other for their own purposes at the same time. Most of the time, there is no sincere romance between the two, each one is strategically putting the moves on the other, trying to seduce them to join their side, give them information, or obtain the MacGuffin for them. As such, this is often one of the Espionage Tropes. Often, Duel of Seduction ends in a Sex Face Turn. In the mean time, it's a good opportunity for copious Fan Service.

There is a bit of a Double Standard with this trope. Because it's a woman with a lot of sexual experience and drive is a lot less socially accepted than a man with the same, more often than not the seducer is on the side of good, and the seductress on the side of evil. The seducer is more likely to convert the seductress to his side in the end, and she often loses much of her power and appeal in the process because Good Is Dumb.

Examples of Duel of Seduction include:

Film

How about that scene in Pirates of the Caribbean: Dead Man's Chest? Elizabeth Swan and Captain Jack Sparrow, each trying to get the other to do something in return for something else. She wants to prove he's not as bad as he pretends, he...well, his motivations seem transparent, but on the other hand, it's J a c k.

Live-Action TV

The Star Trek: The Original Series episode "The Enterprise Incident." The seductress is a Romulan Commander Worthy Opponent, and oddly enough, the seducer is not Kirk, but rather Spock.
Gossip Girl - Chuck and Blair, nearly all the time. Subverted as they do in fact actually love each other but are just incapeable of admitting it to each other and are/were infact, the most popular pairing on the show. Blair is also not portrayed negatively or evilly.
In Firefly, a good one between Inara and Saffron. Both recognize what is going on.

(Klaxon Sounds)
Inara: I guess we've done enough lying.
Saffron: You're good.
Inara: You're amazing, who are you?
Saffron: Malcolm Reynolds's widow.

Literature

Dangerous Liaisons
Frank Herbert's Heretics of Dune. Murbella tries to use an Honored Matre technique to seduce and mind control Duncan Idaho's ghola, but his secret Tleilaxu conditioning allows him to seduce and condition her instead.
- They actually manage to condition each other, and end up collectively running off to do their own thing at the end of the series.
In The Demon Princes final volume, Alice Wroke is under orders from the villain to seduce the hero. He, being several steps ahead of the game, obligingly plays along. Although he doesn't sleep with her.
Implied to have happened in two of the Lord Darcy stories. In one, a female spy zaps Lord Darcy with an infatuation spell. Darcy realizes what happened, and spends the night letting her get false information out of him.

Music

The song Conquest of The White Stripes: [1]

Tabletop Games

An ancient Dungeons & Dragons joke: Once Upon a Time there was a young lad and a young lass, wizards' apprentices. They decided to exchange some magics. Both cheated and cast Charm Person to ease the bargain, and both failed their saving throws horribly. They lived Happily Ever After and even died the same day.

Video Games

Knights of the Old Republic plays the hell out of this one in the trial scene on Manaan. It starts as a straight up version of this, then gets interesting.
An interesting version (with Psychic Powers) turns up as Samara's loyalty mission in Mass Effect 2. Shepard is required to catch the attention of Samara's daughter, Morinth, who kills people by sleeping with them. This requires three steps: first draw her attention by making a scene in her favorite bar (punch people, stare down a krogan, dance really well), then pique her interest in conversation, and then she takes Shep back to her apartment and tries to turn her telepathic abilities against the commander, who tries to resist through sheer virtue and/or badassery. It's possible to blow either the second part (in which case she walks out and you fail the mission) or the third ( she draws Shep under her spell and is about to strike when Samara blows the door in). Oh, and Morinth is an asari, so Shepards of either gender can participate.