Dark hair and pale skin as an indication that a character is beautiful. In western culture, this is a once-dead, now reviving trope, thanks to the Goth and Retro movements bringing an increased awareness of this and the 1950s pin-up style regaining popularity. In addition, the current vampire fad and the rising fear of skin cancer have helped with the resurgence of this trope. This is also quite popular in Eastern media, being the traditional standard of Asian beauty, and the fact that most of the Japanese population has black or very dark brown hair helps. The high contrast also makes for a striking and visually appealing appearance.
Commonly a requirement for the Yamato Nadeshiko type and is also known as the Yamato Nadeshiko look. In fact, a Raven Hair, Ivory Skin Yamato Nadeshiko is a stock character for the Harem Genre.
There is crossover between this look and Eerie Pale-Skinned Brunette, in the form of attractive Goths, beautiful vampires, and other characters who manage to be both creepy and beautiful.
Contrast Eerie Pale-Skinned Brunette, where this look is seen as, well, eerie, and But Not Too White. Compare Dark-Skinned Blond, its visual inverse.
And please, people, before adding to this list, consider whether or not the character was clearly meant to be attractive, explicitly stated to be attractive, and/or regarded as attractive by any other characters. Do not add them to this list just because you find them to be attractive.
Black Butler: Sebastian features this stunning contrast, and that's part of the reason why he has so many admirers.
Black Jack: one episode featured a strong example of this — Souno, a young girl from an old and rather traditional Japanese family, who had been kept indoors all her life due to suffering form a debilitating disease that would cause her life to drastically shorten if she was exposed to sunlight (as well as killing her off before she turns 18 even if she avoids it). She's spent most of her life in a sealed room, practicing Ikebana, the Japanese art of flower arrangement, under the watch of her very severe Overprotective Dad; thus, Souno is perfectly pale, with perfectly black hair, and a perfectly exquisite face...a beauty in a bottle. (Remember, the "Nadesico" part of Yamato Nadeshiko refers to a particular type of flower — probably a deliberate parallel) Fortunately, Doctor Blackjack is there to help — along with his lively assistant, Pinoco, who strikes a really cute Inter Generational Friendship (sorta) with Souno and gives her the courage to get the treatment she needs.
Negi is awestruck when he accidentally spies on Setsuna in the bath, because of her incredibly pale skin and raven-black hair. Chamo even refers to her as a Yamato Nadeshiko due to her looks! She later turns out to be a Heroic Albino; her hair is dyed to fit in better.
Konoka is also seen as this when she wears a kimono to school.
Homura of Puella Magi Madoka Magica. There's a lot of impressed gasping when she first walks into the classroom, and Sayaka comments on how beautiful she is.
This trope is quite popular in 1950s pin-ups, and modern women like Dita Von Teese have helped bring the art style back to life.
Death and Desire from The Sandman qualify (two other members of the Endless have the right hair and skin for it, but Morpheus is extremely gaunt and Looks Like Cesare and Despair is a Gonk); Death was based on a myth (Kabbalistic, I think) in which the Angel of Death appears to the deceased as a woman so beautiful their soul leaves their body in ecstasy, and, being the personification of desire and all, Desire is (supposed to be) the embodiment of perfect androgynous beauty.
Domino and Sage from X-Men; Sage has a natural but pale skintone while Domino's skin is literally white except a black patch over her right eye.
Arwen, being the most beautiful woman alive, has dark hair and pale skin (as in the book).
Frodo is a male version of this trope, as he is a Pretty Boy with pale skin and dark hair as far as the film adaptations are concerned. In the books, hobbits are more pleasant-looking than beautiful. Then again, Frodo is explicitly described as fairly good-looking for a hobbit.
... there she stood, raven-haired and violet-eyed, snowy fair and finely fit, as if carved by the gods from a solid block of desire.
Isa, from Only Echoes Remain is a gorgeous goth girl despite being homeless on the streets of an alternate-universe version of Chicago. This is entirely the result of her being a mystical being created by a precocious teenage sorceress who designed her to meet or exceed her own standards of beauty. White-pale skin, very, very long night-dark hair, and a flawless face and body were her gifts to her creation—along with a true form that is effectively a demonic manifestation of darkness and death.
The Gemma Doyle Trilogy's Pippa is renowned for her beauty and fits this trope to a T.
J. R. R. Tolkien's use mixes Author Appeal (his wife Edith was a fair-skinned brunette) and, presumably, Celtic notions of beauty, since the ancient Celts (flanderized as Fiery Redheads) were actually mostly dark-haired and apparently regarded this as the ideal — thus most of Tolkien's most important beautiful characters are dark-haired and pale-skinned, with gray eyes. For one thing, most elves look this way, and elves are always tall and more beautiful, more healthy, and more physically perfect than is humanly possible. Then some elven characters stand out for their especially emphasized dark-haired-pale-skinned beauty — Lúthien in The Silmarillion, the most beautiful woman in the world who also happens to be half-angel, and partly based on JRRT's wife; and her part-human Heinz Hybrid descendant Arwen in The Lord of the Rings, who's reportedly the second-most beautiful woman in the world.
Romance of the Three Kingdoms: the Qiao sisters were this, and the book plays up that part of the reason Chi Bi happened was that Cao Cao was after them because of this trope.
Many tragic heroines in 18th century Gothic Horror novels are described this way.
Yennefer from The Witcher books. She is pale with raven black hair and wears only black and white. Like all sorceresses, she is incredibly beautiful.
Irene/Attolia from The Queen's Thief is one (fair skin, very beautiful, dark haired).
Inverted in Fairest with Ava, described to have black hair and pale skin, but is ugly.
Several of Robert E. Howard's Conan the Barbarian stories use this trope. Many of the women that Conan becomes involved with are described as having dark hair and pale skin, some of the more notable ones being the pirate queen Belit and the slave girl Zenobia.
The breath-taking Sidhe Queen, Mab is usually pale with silvery hair and green eyes, but her hair and eyes (and clothes!) turn black when she's truly angered. Makes sense, as she represents Air and Darkness. Titania, on the other hand, retains her pale colouring but her rage is more explosive as the Summer Queen.
Tom Riddle (AKA Lord Voldemort) from Harry Potter had pale skin and dark hair, and was frequently noted to be very handsome before he started ripping out chunks of his soul and putting them in Horcruxes. Harry himself can be considered another male example, having black hair and all.
There's the princess Thayet jian Wilima of the Tortall book, Lioness Rampant. Her face-particularly her nose-was strong boned; her hazel eyes were deep-set under even brows; her chin was determined. Her mouth was naturally red, accented by ivory skin. She wore her jet-black hair pulled into a knot.
Barmaid: Mmm, you're an handsome fellow. Arthur: Well, just wouldn't be the first to say it. Barmaid: Oh. No, sorry. I was talkin' about your friend here. (Looks suggestively at Merlin.) Arthur: (shocked) Him? Merlin: (smirking at Arthur) Thank you.
Lila (Jamie Murray) from Dexter, Dexter's psychotic girlfriend from season 2 has back hair and extremely pale complexion. Angel describes her as a perfect porcelain doll and says that with skin like hers, she should stay outside the beach and sunshine. Dexter's sister Debra offers a different perspective. She says she's pale like a fucking corpse, and compares her to a vampire several times.
A male example is Naoise, lover of Deirdre in the Ulster Cycle of Celtic Mythology.
Deirdre:(After seeing a raven drinking blood out of the snow) I will love a man with hair the color of the raven, skin as white as snow, and lips as red as blood.
Unlike Snow White this does not turn out at all well.
In Persona 4, Yukiko Amagi is seen as this and gathers quite a fan club because of her looks.
If someone in Fire Emblem 7 is about to describe a Morph, there's likely three features to be mentioned: "1. Pale skin, 2. Hair like ebony (though it really looks purple), and 3. gold eyes". Sonia was actually made to be beautiful and to seduce Brendan Reed.