Virgin Tension

Virginity in women is highly prized. The loss of virginity, on the other hand, is not. Even if it's from rape or abuse or other things that aren't their fault. This distinction doesn't always get made, and the prospect of a heroine losing her pure Virgin Power is often treated as on par with her dying (if not, indeed, A Fate Worse Than Death).

So movies will often go out of their way to indicate that, against all odds, their Damsel in Distress is still a virgin, just to add that extra layer of tension. Doesn't matter whether they're prostitutes or in relationships with sexually active people. They're virgins, and damn it, the script will make that EXCEEDINGLY clear to make the audience worry: "Oh no! Will the pure chaste maiden be devirginized? Say it isn't so!" This can happen with a My Girl Is Not a Slut moment or just with dialogue.

Compare Their First Time, Virgin Power, Nature Abhors a Virgin, Defiled Forever.

Anime and Manga

 * In Fushigi Yuugi, Miaka ends up knocked out, with the villain expressing his plans to rape her at the time. When she wakes up, she assumes the worst, especially since it would mean that she can't summon Suzaku anymore...thankfully, nothing actually happened to her.

Film
"Joe Friday: "blah blah blah Connie Swail." Pep Streebeck: "Wait a minute! Connie Swail?! Don't you mean the virgin Connie Swail?!""
 * Taken. Kim's been kidnapped by all kinds of sex traders, but remains a virgin. The movie goes out of its way to point out how she's "certified pure." Justified in that it would have gotten them a higher bid for the opportunity to "deflower" her, and wanted to keep her in "mint condition."
 * Slumdog Millionaire - Latika becomes a prostitute - but see, they mention she's still a virgin! When Jamal tries to rescue her, he's told: "Do you know how much this little virgin is worth?"
 * To be fair she was being trained to be a prostitute and had not started yet. They were probably planning to sell off her virginity for a high price.
 * Also subverted later, when (it is heavily implied that)
 * Parodied in the 1987 film of Dragnet where everyone always refers to Connie Swail as "the virgin Connie Swail". Except right at the end after she's spent an evening with Joe Friday.

Literature

 * Somewhat interesting used in David Eddings' The Tamuli, when we get the backstory of Mirtai... a member of the Proud Warrior Race, the Atans. She was kidnapped by Arjuni slavers when she was just a child, and spent virtually her entire life as a slave - a beautiful, female, golden-skinned slave. However, she sheer ammount of Badass In the Blood she has, has ensured that anyone who tried to take advantage of her wound up messily dead. As such, she's still a virgin, and intends to remain that way 'till she's married. As she tells her paramour, Kring, when he suggests making an 'early start', "I've killed too many people in defense of my virtue to waste it on 'almost married'."
 * Justified in Stationery Voyagers: Final Hope. Laura's virginity is the only thing that permits her to reincarnate so often. She is actually relieved to be killed in the line of duty rather than captured and detained, specifically because it increases her odds of returning that her enemies don't have time to consider rape as an option.
 * In The Sword of Truth series of books, Confessors are forced to remain virgins for the safety of their would-be lovers: the man's mind would be destroyed when the Confessor's power is released during the act of passion. Confessors therefore choose their eventual husbands not based on love or desire, but simply based on the need for procreation to pass their powers on to the next generation. The husband has his mind stripped away and becomes not a lover, but a mindless slave whose sole purpose is to teach his child everything he can. Of course, the main characters eventually find a way around this.
 * Invoked in the Witch World books by Andre Norton. Witches (at least in the first few books) are traditionally virgins, and men who plan to capture them usually have a few ideas on how to rob them of their "powers". However, since witches are good at defending themselves, this rarely works.
 * The number of virgin widows in historical romance novels is truly mind-boggling.
 * The Inheritance Cycle never mentions the word "rape," but still informs readers that Arya was not taken advantage of while captured by the Empire, because she used her magic to fight the men off/make them impotent. Even though she was unconscious. Or...something.
 * In Juanita Coulson's The Death God's Citadel, this trope is first invoked and then subverted.
 * Witches in the world of the Black Jewels can be "broken" and stripped of their power if their Virgin Night is not performed with care. After a certain age, young women can have the ceremony, but until then a virgin is highly vulnerable. Averts "undesirable loss of virginity" in that a properly performed Virgin Night will secure a witch's power, while still playing up the "fear of possible deflowerment" part of the trope (as in The Invisible Ring, when the hero realizes that the heroine is a virgin and flips out about the risk she's taken.)

Live Action TV

 * Heroes Fanon has an unhealthy obsession with Claire's honor. While the writers remain coy about her status, fans keep going on about how her regeneration abilities might leave her with "perpetual virginity" no matter how many times she might have sex.
 * Similar to Heroes, Jessica from True Blood was turned into a vampire (against her will) and everyday returns to the status she was turned as. It is explicit (and a minor plot point) that she "re-virginizes" after each time. Like Prometheus, this is a bad thing for her, as sex with her boyfriend will always be painful.
 * In any case, "virgin" means "never had sex", so neither of those characters are virgins regardless of their hymens. Some actual virgins get their hymens surgically removed so as to avoid a painful first time, and some kinky non-virgins (or women trying to avoid punishment by their culture for not being virgins) have them reconstructed.
 * The hymen can also be destroyed via an injury (such as falling off a bike) and most girls this happens to never realize it.
 * Both of these examples are somewhat bizarre, as - contrary to popular belief - the hymen is not actually something that is supposed to be "destroyed", but rather a membrane that needs to be stretched out for a woman to have comfortable sex. Because most people don't realize there are precautions you can take, stretching the hymen often involves painful tearing and bleeding, creating the illusion that damaging the hymen is a necessary evil for every woman's first time. Fridge Logic comes into play when you wonder why an immortal vampire never thinks to use lube and/or ask her boyfriend to take it slow, methods of preventing hymen tear that have existed for years.
 * Daytime Soaps are fond of this trope, especially Days of Our Lives.
 * The then virginal Hope Williams (she's a grandmother now, Days is a Long Runner) spent several months managing to avoid consummating her forced marriage to Larry Welch by claiming she was pregnant by her true love Bo Brady. Needless to say when Bo found out about the lengths Hope was going to in order to avoid Larry's advances, he was thrilled. After Bo and Hope had a secret getaway to New Orleans behind Larry's back there was no more tension.
 * Carrie Brady was the victim of an Attempted Rape by amasked man on the night that she was supposed to lose her virginity to her true love Austin. One of the suspects in Carrie's attack was her ex boyfriend, Lucas Roberts, who would've been successful in his earlier attempt to bed Carrie had not his true motives for dating her been exposed. However, the culprit turned out to be Alan, another of Carrie's rejected suitors. Notably, once Carrie finally did lose her virginity to Austin, Alan lost interest and eventually raped Carrie's younger(and still virginal) sister Sami instead.

Theatre

 * Marina in William Shakespeare's Pericles, Prince of Tyre is captured by slavers and sold to a brothel, and manages to remain a virgin as everyone who meets her is instantly reformed by the sheer force of her goodness.
 * Except, of course, the slavers who captured her and the owner of the brothel.

Web Comics

 * Candi Levens of the Ciem Webcomic Series is pointed out explicitly to not lose her virginity until she meets Denny Levens, no matter how many men have tried to rape her. The books subvert this. A Super Gangbanger and a Vampire both force themselves on her; but she is always able to fight them off before they can reach orgasm. Of course, she ends up having to kill them for one reason or another, which she's not very happy about.
 * Her escape efforts usually lead to her assailants getting themselves killed somehow, hence why she vows to be a little more careful when she becomes Ciem about not racking up too large a body count. (But even when she doesn't actively put them in the line of fire, her enemies often die by their own stupidity anyway.)