Boy meets buxom girl symbiotically joined to a demon sword and controlling a pseudo-zombe horde.
A typical Franken Fran story usually doesn't start with this as a premise, but that may be how it ends up.note Boy Meets Girl, girl gets in a car accident, remainder of girl's body placed in giant bio-reconstructive chrysalis to regenerate while boy helps nurse her back to health, girl emerges seemingly unscathed from chrysalis, boy and girl head to love hotel, girl transforms into monstrous insect creature and eats boy's head, reader is now horrified.
My Lovely Ghost Kana: Boy meets Cute Ghost Girl haunting his new apartment. Boy drowns his sorrows. Boy has long conversation with ghost about life and death. Boy accidentally gropes ghost, somehow. Ghost is surprised, then excited at the implications of a living boy being able to touch her. Boy and ghost make sweet love, then begin a bizarre, surprisingly tender romance in the apartment where the girl brutally killed herself many years ago.
Gosunkugi from Ranma ½ developed a crush on Kogane while they spent time together during an episode. But at the end, he gets over it and continues to stalk Akane.
She had to return back to the netherworld at the end of the episode, as she can only manifest one day a year, but it's implied that he'll still be waiting for her until then.
Rosario + Vampire: Boy meets vampire; she turns him into a ghoul, albeit accidentally. For some reason this doesn't threaten the relationship at all, despite creating the extreme likelihood of him turning into a mindless berserker.
Sankarea: Boy obsessed with the undead meets girl, girl falls off cliff and dies, girl becomes zombie, zombie-girl becomes freeloader in boy's house.
3×3 Eyes: Boy meets immortal, boy killed by immortal's pet, immortal absorbs his soul to resurrect him as a zombie—ahem—Wu.
Living Dead: Boy meets girl and develops a crush, but can't work up the nerve to tell her. Girl dies, becomes a zombie, and moves into boy's home.
Tasogare Otome X Amnesia: Boy meets girl. Girl turns out to be amnesiac ghost of a 50 year old corpse in the school basement. Mysteries ensue.
Wirbelwind: girl meets ordinary boy (initially), who then turns into undead, but it's all to the better because she's a Dark Elf and now they don't need to Wangst about their lifespans and incompatible alignments and just adventure together. And fuck, of course, because that's an ecchi adventure manga by the famous H-artist Makoto Fujisaki.
The Voynich Hotel has two separate relationships: Professor and Tenebraum, and Mr. Haraki and Mercelo.
The main plot of Tokyo Pop's original English language manga My Dead Girlfriend.
Madman has a normal girl in love with a dead guy who looks weird enough in the costume he almost always wears, but beneath that mask is a person who looks very much like a corpse.
In the Cherry Comics parody of Anne Rice, Cherry and Ellie have sex with a vampire, a mummy and a ghost.
Hivefled: Gamzee has exchanged flirtatious comments with Laneen, the ghost of a troll who is probably his half-sister. Trolls lack an incest taboo, which doesn't help much, especially since both of them were sexually abused by the troll who turned out to be their mother (or as close as one can get to one with troll reproduction) and said mother killed Laneen.
Tim Burton must like it a lot - Beetlejuice tries to marry the 16-year-old Lydia in the movie. And while the series avoids actual romance between a dead guy and a 12-year-old, the level to which he is obsessed with her shows exactly what Tim had in mind for the two of them.
In one early episode, we see Beetlejuice has a huge shrine devoted to Lydia in his head. In another he gets split in two and starts fighting himself to impress her - he stops when he realises he's upsetting her. In another he gives Prince Vince excellent advice on how to court her, and then becomes incredibly jealous when it works very well.
Let the Right One In: Young boy meets apparently-young vampire, and, as with the movie version, puppy love + carnage ensues.
The Vampire's Beautiful Daughter: Rebecca is a half-vampire, and has to choose between undeath with her father and vampire friends or a human life with her human boyfriend Johnny. The story is told from Johnny's point of view.
Somewhat different, as well, in that it is also boy-meets-something. His fascination with her arises from his inability to understand what exactly she is, since she appears to have some level of psychic abilities and intimate knowledge of a world she has never personally experienced, as evident through the accuracy of the novel she has had published about Aubrey himself.
The Peony Lantern: Boy meets ghost. She takes him with her. Although it may have just been an elaborate hoax made up by his servant so he can steal a solid gold talisman from the local temple.
Anna Dressed in Blood: A ghost-hunting teenage boy travels to a new town to dispatch a particularly troublesome ghost. They fall in love instead.
Ancient Chinese literature quite often features stories of men falling in love with fox-spirits or ghosts (or, in one case, living quite happily in a three-way marriage with a fox spirit and a ghost). At least one story features a man having sex with the spirit of a butterfly (although she was in human form at the time).
Chronicles of a Reluctant Necromancer: Protagonist necromancer raises dead girl back to life, who happens to be an assassin too, girl tries to seduce necromancer but eventually falls in love with him.
Fafhrd and the Gray Mouser: Fafhrd's ghoulfriend Kreeshka. Minor twist in that Leiber's ghouls are a race, not undead humans. Still, they look like skeletons with organs over them and they eat human flesh. Plus, they're "ghouls."
You know what, it's likely much safer to just claim that every main character has fallen for this trope. This show was weird that way.
The ABC/BBC co-production Dead Gorgeous plays with this by having "Living Ghost" Rebecca fall for living boy David. However, he seems to not be particularly interested.
The vampire detective show Moonlight features the romance between the main character and his human love interest.
In Vampire Diaries, Stefan and Damon both meet Katherine. A few hundred years later, Stefan meets Elena. Then, Jeremy and Vicki, after she becomes a vampire. And then Jeremy meets Anna, though initially she was just using him.
The Masters Of Horror episode "Jenifer" is a quite brutal deconstruction. Boy warms to Ghoul first out of pity, then becomes sexually obsessed with it. Ghoul pretends to love Boy to provide for it while Ghoul keeps murdering people.
"I Walked with a Zombie" by Wednesday 13 and "She was the Teenage Zombie" by Murder Dolls. A lot of their other stuff qualifies, too.
"A Boy, A Girl, And a Graveyard" by Jeremy Messersmith, though the ghost in this case is male.
"The Zombie Song" by Stephanie Mabey. "I'd never eat your brain, I just want your heart."
"A Romance with the Grave" by The Vision Bleak. Literal example. 'Ruthless lust without disgust, dirt and dust, a romance with the grave'
Alice Cooper loves this trope. "Cold Ethyl" is a more "subtle" example, while "I Love the Dead" drops any pretense.
Alex Day also uses this in his song "She Walks Right Through Me"
A possibility for characters in Promethean: The Created, especially Galateids. On some occasions, it might help with a Promethean's Pilgrimage, but more than likely it will end very badly, thanks to their Disquiet.
Neverwinter Nights has Boy meets Ghost Paladin. Somehow, none of the issues that would create ever come up in the game, though it is implied that she gets a new body after you return to the world of the living.
One minor sidequest in Skyrim has you searching for the journals of the necromancer Arondil. As you search the barrow he is currently squatting in, it's impossible to ignore the fact that it's populated entirely by female Draugr and ghosts. As you read his journals, it becomes clear that Arondil's interest in the female undead wasn't entirely scholarly. Apparently he finds the feel of ghostly ectoplasm arousing. Eventually you get to the end of the dungeon and find a double bed... with a female ghost "sleeping" in it.
I Saw Her Standing There has this as its premise. You have to lure a zombie girl to a cage in each level, with each "act" introducing a new gameplay twist. All the while, there is narrative text describing the love between the main characters.
Taiga in Duel Savior Destiny is initially thrilled to receive the confession of love from the cute Nanashi, but this turns sour when her arm falls off and she invites him back into her crypt. Despite the bad beginning, they actually get along decently well. She also has a route, where it seems that half the reason Taiga isn't willing to sleep with her like he would anyone else isn't just because she's cold and dead, but rather because she lacks much in the way of a sense of touch and wouldn't enjoy it. But hey, that can be fixed. And it turns out she's not a zombie, she's a homunculus.
In the aptly-titled Visual NovelRomance Is Dead, lucky Madeline gets not just one undead love interest but three: a zombie who's magically compelled to stay close to her, a very French vampire, and a friendly ghost.
Sluggy Freelance: Torg doesn't initially know that Valerie is a vampire, and even after finding out, he initially thinks that un-living with her forever wouldn't be that bad. But by the best guess, it isn't real love in either direction, and in any case he chooses to destroy her rather than turn against his friends.
Unlife Is Unfair is about the other way around, a nice zombie (nando) meets a girl and falls in love of her. She only wants to be his friend though. Later on she discovers feelings for him, which can be kind of harring.
Strictly speaking, she is never shown to have any romantic or coital interests in her own creations (whom she IS shown to regard as her children). She is only shown to have romantic designs for Xykon. And mentioned "that crypt thing" she didn't know was female, so presumable not her either.
In Negamaki Chief Buffalo Jerky's friend Maize spends a lot of time dwelling on this. Despite both of them being dead, she's interested in pairing the Chief off with Negamaki and asks Tamago to call her if he survives being attacked by the hell-moose.
Danny Phantom: Gender-flipped , in this case Danny is (obviously) the ghoul and Sam is the Boy. I mean girl. In this case, though, Sam and Danny were friends long before he became half-ghost.