Sleeps with Everyone but You

The difference between a slut and a bitch?
A slut sleeps with everyone.
A bitch sleeps with everyone but you.

So there's this one girl. You know the one. The one who Really Gets Around. She'll jump into bed with just about every guy who asks. She...well, she just really likes having the sex. You get the point.

But this girl, who will schtup men, women and most species of plants, is utterly unobtainable for this one character. That character doesn't have to be the protagonist, and, in fact, rarely is. Most of the time this is used to demonstrate that the character's sad and pathetic; after all, if Betty Bangs-A-Lot won't kiss him, he must be pretty crummy at this life thing. This is almost always used as a comedy gag, largely because it's too depressing to contemplate under any other circumstances. Think of it as Even Sluttiness Has Standards.

More rarely, on the other hand, it can be used to demonstrate quite the opposite. Sometimes the reason the promiscuous character refuses to have their usual mindless, consequence-free sexytimes with one target is that just this once, they're holding out for something more meaningful.

Note that pronoun-laced description aside, this trope works perfectly well with Manwhores.

No real life examples, please; this is All The Tropes, not Tropes After Dark.

Examples of Sleeps with Everyone but You include:

Anime and Manga

In Panty & Stocking with Garterbelt, Panty has sex with nearly everyone but Brief. She did offer him sex once, but Brief thought it was going too fast. Panty dropped the option right then. She does try and do it with him once she finds out that he's Beautiful All Along, but by then her hymen's rebuilt and damn-near impenetrable. They finally do the deed in the last episode, which restores her powers.

Comic Books

In Neil Gaiman's 2006 relaunch of "The Eternals", Sprite, while explaining that his motives boil down to being really sick of being stuck in a prepubescent body, notes that he's the only male Eternal with whom Sersi hasn't slept.

Fan Works

The Neon Genesis Evangelion H-Fanfic The A.L.I.A.S. Vignettes has Asuka finding a really creative way to torture Shinji: whenever she has a date, she drags the poor shmuck back home, throws Shinji out of his room then does the deed in there, knowing full well that Shinji is within earshot. And she's not doing this because she's a slut, she's doing this purely out of sadism.
A major plot point of the Naruto Fanfic That Look, in which Anko sleeps with everyone in Konoha but Naruto, and even reacts violently whenever he so much as touches her... After she gets him drunk and climbs naked into bed with him. And she seems to believe that he's in the wrong when he disapproves of her actions.
In multiple Naruto fics where Naruto is a God Mode Sue with a harem, Sakura usually doesn't fall for him. And That's Terrible.

Film

Kiss Kiss Bang Bang: Harmony slept with everyone except Harry when they were in school together. (Even Chook Chutney!)
In Dogville, Grace is raped by everyone in the village, but turns down Tom (who doesn't want to rape her - he genuinely wants to make love to her) whenever he asks her to sleep with him. He fails to understand why, because he considers himself an intellectual and refuses to see anything on an emotional level.
This is a major plot point/source of gags in The Man With Two Brains. After Steve Martin marries Kathleen Turner's Gold Digger, she won't consummate the marriage, but she'll do just about anyone else.
Boogie Nights: Little Bill's wife.
In the movie Innerspace, nebbish hero Jack Putter's dysfunctional love interest Wendy idly remarks on the irony of her sleeping with just about everyone he knows except him when he's the one guy she might actually like. At the end, after he's taken a level in badass and she tentatively suggests they start dating ("Jack, I think we should try dating. Maybe not exclusively at first, at least for me, but... "), he brushes her aside with a quick "not a chance" before moving on to his next adventure.
In Trucker, Runner calls Diane out on this fact, although her reason for not sleeping with him is a pretty damn good one considering he's married, but his frustration comes from her blatant refusal to acknowledge the fact that they have a thing for each other, not simply because she won't sleep with him.
In Jingle All the Way, Sinbad's character, a mailman, complains about having to pay alimony to his ex-wife, who slept with everyone at the post office except for him.

Literature

A Song of Ice and Fire: A side character (whose face is covered with boils) reminisces about his boyhood in a small village. As a teenager, he spent hours gathering flowers for a girl in the village who had the "town slut" reputation. When he presented them to her, she laughed at him. So he killed her.
The Culture:
- In Use of Weapons, Diziet Sma, The Handler, is definitely a Good Bad Girl (which makes sense, since The Culture is the epitome of Fetish Fuel Future). That being said, the one person she won't sleep with is the novel's other protagonist, the sociopathic badass Zakalawe. It's hard to tell if this is because she wants to keep the relationship professional or is somewhat turned off by him. But it's not for lack of trying on his part.
- This is part of what drives the protagonist of The Player of Games so nuts that he embarks on the epic journey that constitutes the plot. It should be noted that this is in The Culture, which is ridiculously sexually liberated (the hero is widely considered a bit odd because he has never changed sex!), which makes the snub even more annoying than usual.
There's a short by Fukazawa Shichiro with this premise. The main character is a Jinmu (a derogative term for second born son), in a village where second born are treated like livestock (they aren't even allowed to heve sex, ever). One man who feels guilty for killing a Jinmu once, leaves a will behind before dying declaring that his wife must sleep with every Jinmu in the village. Guess who's the only one left out.
In the novel Super Folks, David Brinkley's ex-crush is known to have slept with every superhero except him. In this case, however, it wasn't because of any sort of disgust (indeed, it's implied she would have, if he'd tried) so much as him never thinking to go for it.
In The Sun Also Rises, this is true between Brett (the girl) and Jake. Zigzagged in that they are in love with each other, and Brett would very happily jump his bones if he hadn't lost them to some sort of war injury.

Live-Action TV

In Lexx, Zev/Xev is a love slave with an unslakeable libido - but she refuses to have anything whatsoever to do with Stanley, whom she sees as repugnant. Ironically, she herself fails to bang anyone, since her choice of lovers tend to be killed, are already dead, is a disembodied robot head, or is Stanley.
Stuart in the British version of Queer as Folk will sleep with anyone (once) except Vince. Vince's mother says it's because Stuart's "saving him" for when they're both old. They do eventually settle down with each other, but it takes the run of the show to get them there.
- Happens in the US version as well. Though Michael gets over Brian eventually, and they both settle down with other people.
Gina from The George Lopez Show will sleep with Anything That Moves... anything, that is, that can get past the initial nausea. At one point, Ernie decides he's finally gotten desperate enough to make a pass at her, which she turns down.

Gina: I guess I have standards. Hey, I'm as surprised as you!

Male example in Owen of Torchwood. He sleeps around quite a bit, even having affairs with two of his coworkers (one of whom was in a relationship at the time), but never even notices Tosh who is madly in love with him. He even calls her on it in "A Day in the Death."

Owen: For some reason you want me. You know I don't know why, but you always have -- always looking at me, watching me screw all those other women, your heart breaking.

Subverted on Frasier. Roz gets all over every man as soon as she sets eyes on him, but doesn't get with Frasier. However, both of them know this is because they don't want to hurt each other's friendship. In fact, when she finally does have a fling with him, both of them panic about it the next day.
- This is explored in one episode when Rox starts a relationship with a psychiatrist who mentored Frasier through college and who is similar to him in many ways, prompting Frasier to be uncomfortable around him after he inadvertently catches them together at her apartment one night. He comes to realise that he's actually sublimating his jealousy about this trope (although she gets tetchy when he initially tries to phrase it in these terms), since he'd previously been able to comfortably rationalise the situation with the assumption that he simply wasn't her type but has now received confirmation that he could be.

Roz: Frasier, did you ever stop to think there may be something special about not being picked?
Frasier: Roz, that didn't work when I was cut from pee-wee football, it's not gonna work now.

The Waitress in It's Always Sunny in Philadelphia will slip into anyone's bed when she's drunk, even Frank's. Anyone except Charlie (inverting Romance on the Set, since they're married in real life.)
Laurie from That '70s Show, after marrying Fez, refuses to sleep with him. She'll sleep with everyone else during this time and he calls her out on it. Ironically enough she did sleep with him once and only once, before they married.
Occurs in the Cold Case episode "Rampage".
In the first season of True Blood, Jason Stackhouse will pretty much bang anything female... except Tara, who has a huge crush on him. Of course, considering what happens to the rest of his conquests, that may not be a bad thing for Tara.
A victim on an episode of Psych would have sex with everyone but the killer, who was more or less a Stalker with a Crush , resulting in said murder.

Mythology & Folklore

Classical Mythology (and all variations thereof) gives us Aphrodite, who was widely known for bedding gods/mortals/anything with a penis EXCEPT her husband Hephaestus. Zeus dodges this by taking the "Sleeps with Everyone AND You" approach when it came to Hera (though it didn't help much in Hera's eyes).

Tabletop Games

A very special porn star in Unknown Armies.^[context?]

Theater

In Seminar, the only guy Izzy doesn't sleep with (at least during the course of the play) is Douglas. This is rather ironic, first because Izzy is using Douglas for his connections in the literary world, (and you'd think a little action would make that easier) and because Douglas is probably more attractive than the other guys in the play. (And unlike the teacher she sleeps with, isn't old enough to be her father).

Video Games

In Too Human, Freya (Goddess of Love) rightfully has a reputation for jumping in bed with just about anyone, and indeed goes to some length to lure the main character to her bed (unsuccessfully, but that's mostly because he's too busy trying to avenge his recently-dead wife). The only one who actually calls her out on this, however, is the ever-brash Thor, who refers to her as 'The whore of the Gods', and accuses her of having 'been' with every man in the hall (it was during a council-meeting of the entire Aesir Corporation.) To this, she snarkily replied "Aye, I've been with every man here, but I've not been with YOU. Not that you'd know what to do with me." The hall is leveled with laughter as Thor splutters angrily.
In Darkseed 2, Mike Dawson discovers his murdered ex-girlfriend has slept with pretty much every man in town except him. He doesn't have a very mature reaction to this.
During Act 3 in Dragon Age 2, Hawke encounters Emile De Launcet, a disgusting little man who claims to have escaped the Circle so that he can have sex with a woman. Hawke can offer Isabela's services in exchange for his return to the Circle, at which point Isabela refuses, saying that she does have some standards.

Web Comics

Used several times in Something*Positive to emphasize how ugly Davan is supposed to be.
Jodie in Loserz has slept with virtually every person her age, of both genders, in the entire zip code. Except for her two best friends, Ben and Eric. Oddly enough, this isn't even used to lampshade how pathetic they must be (although they are both geeks): Even at their horniest and loneliest, even if they're all stoned, neither of them seems to even think of asking Jodie for sex, or vice versa. Its just not in their mental universe at all. All three of them are just that deep in each other's Friend Zone. At least it's mutual.
In the backstory of Shadowgirls, teenaged Charon (pronounced "Sharon") was portrayed as going through every bad boy in Innsmouth, while using her best friend, Jackson, as an emotional backstop when those flings inevitably went sour. When Jackson finally has enough and tells her off, Charon tells him that she would've turned to him... eventually. It's implied that they do actually get together later... just in time for Charon to disappear and return, amnesiac and pregnant.
In Magick Chicks Faith seduces Anything That Moves, trying to charm or outright brainwash when someone doesn't like her (like Tiffany and Melissa), or just doesn't show more than polite interest (Layla). The only exception is her secretary Sandi who looks at her with puppy eyes and constantly deludes herself that oh, NOW Faith will notice her - but is invariaby treated as a servant or pet by Faith and as "yap-yap sycophant" other schoolmates. That's not being Oblivious to Love - Faith knows Sandi is jealous.

Western Animation

Clone High has great fun with this with Cleo's many references to sexual escapades, yet Abe has to jump through several incredibly difficult hoops to get anywhere near sex, even after he becomes her boyfriend.
Titan Maximum: Sasha sleeps with just about everyone. And yet, she finds team nerd Willie utterly repulsive. He worships her and dreams about one day touching "her left, or, even better, right, boob!"
Gigi (or G.G., or however it's spelled) from Harvey Birdman, Attorney at Law.^[context?]
A variant in Metalocalypse. Dethklok, being Dethklok, is besieged with women who will do unspeakable sexual things with every member of the band... except Murderface, the bass guitarist so ugly and unpersonable that being in a band that can raise mythological monsters and change the very nature of reality still isn't enough enough to get him laid.
- Not even the female roadies (who are all loyal to the band) will sleep with him.
Family Guy: Seemingly, every teen-aged boy in Quahog will sleep with any teen-aged girl... except Meg Griffin, who is portrayed as so hideously ugly that boys will go out of their way not to have sex with her; several have taken extreme measures to avoid the humiliation of having "scored" with Megan. Usually this is implied, such as the hunk who, after Meg asks him to a dance, fires a shotgun and cries out that he shot his 2-year-old brother.
- Pretty sure he says, "I'd love to Meg, but I have to go to my little brother's funeral."
- Quagmire, who's even made multiple passes to Meg, refuses to have sex with Peter's boss Angela.
In Clerks the Animated Series, Caitlin Bree chases Anything That Moves—even a Ferris wheel in the final episode—but still won't give Dante the time of day.
In Sealab 2021, (white) Debbie will sleep with anyone and everyone... except good-looking but idiotic Stormy. Apparently she once told him she was saving herself for marriage.