Gaston in Beauty and the Beast. Yes, he loves himself more than he'll ever love Belle, but pursuing a girl who hates you, threatening to chuck her father in the asylum, and murdering your rival surely counts. He loves himself so much that it is either incomprehensible or maddening to him that she does not, or just an intolerable affront to his towering ego. "BELLE IS MINE!!!"
In Megamind, the nerdy cameraman has a big crush on the news reporter woman he's normally assigned to film. So when he becomes Tighten/Titan, his infatuation becomes a lot more dangerous.
Arguably, Megamind himself was initially this towards Roxanne since it's hinted the reason he keeps kidnapping Roxanne is because he has a crush on her (in his warped, socially awkward sort of way) and it's his way of being close to her. Unlike the above example, he does get better.
Sally is a relatively benign version of this in The Nightmare Before Christmas, following Jack Skellington around a few times and sending him small gifts. After Jack becomes obsessed with Christmas this turns to trying to protect him from himself, as Jack has the enthusiasm of a thousand passionate actors and the common sense of a wet cabbage.
WALL•E. He stows away on a massive, ominous spaceship with no idea where it's going just so he doesn't have to be separated from EVE. His obsession is probably justified in that until EVE came along, he had no-one to talk to except cockroaches for centuries. EVE was perfectly aware that WALL•E was stalking her due to his bumbling nature, but didn't seem to care, and she was armed with a laser-weapon that could blow holes through mountains. They fall in love with each other at the end. Granted, WALL•E's a robot and most likely doesn't understand how his behavior would look to others.
Film - Live Action
Main character Elliot from the remake of Bedazzled (2000) knows every intimate detail (likes, dislikes, relationship status, etc.) about his coworker Alison, who has no clue he's alive. He doesn't go so far as actually breaking and entering until Satan puts him up to it, but he bends pretty quickly—it doesn't hurt that he's invisible and intangible to do so while she's showering. Then there's the fact that every one of his seven wishes save the first and last one revolve around getting a woman he's never had more than a minute interaction with.
Bobby (played by Fred Savage) in the TV movieNo One Would Tell.
Mark Wahlberg's character David McCall in the 1996 movie Fear.
In the movie When in Rome, Beth takes coins from a magic fountain, making the men who tossed in those coins turn into Stalker with a Crush. They all feel they are in love with her due to the magic fountain. Naturally, the main love interest, Nick, tries to contact her. Hilarity Ensues.
Sandra Bullock's character Mary towards the titular character in the movie All About Steve.
Jacob, the Jerk Ass T.A. in Road Trip is this to Beth. Despite her insistence that they are not, nor ever will be a couple, he acts as though they are and tells Josh that she's "spoken for".
Alex Forrest of Fatal Attraction turns into this after having a one-night-stand with married man Dan Gallagher. As Dan tries to distance himself from her for the sake of his marriage, Alex's actions get increasingly violent, culminating in the infamous "bunny boiler" scene that has her killing and boiling his daughter's pet rabbit.
Hannibal turns the title character into one of these. While in The Silence of the Lambs he simply seems to enjoy being creepy for creepiness' sake, the sequel turns it into a kind of weird romantic love for Clarice Starling, with him sneaking into her house and watched her sleep (while touching her face and hair). In a deleted scene, he breaks into her car and licks the steering wheel to get the taste of her. Plus the part where she's talking to him on a cell phone trying to find him, and it turns out he was behind her touching her hair. The weird thing is that it's actually meant to be romantic.
Alec Baldwin's character, Teacher, from The Juror (1996) is a textbook example of this. He bugs Annie Laird's house so he can listen to her every move, copies and enlarges photos of her and kisses them, and sneaks a bouquet of flowers into her house without her knowledge. When it looks like she won't listen to his orders, he threatens to run her son over with his car, and sleeps with her best friend (promptly killing her afterwards).
Miles Haley from Perfect Stranger. He sneaks into Rowena's house and watches her make out with her boyfriend, tries to flirt with her in instant messaging by posing as someone else, and has a freaky shrine dedicated to her in his house.
Moulin Rouge!: "Satine will be mine! It's not that I'm a jealous man! I just don't like other people touching my things."
Made even more obvious when he orders a hit on his love rival.
Played for laughs in Blades of Glory, with Nick Swardson stalking Jon Heder's character.
"He likes food and dreams and whispers... his favorite movie is Short Circuit... and Fried Green Tomatoes. "
Mark verges on this, no matter what the fans say. You're telling me it's not creepy to film a wedding with extreme close ups of the bride throughout? The time he shows up at their house is odd too.
At least in his case he knows that his feelings are wrong and that he shouldn't have done that (since he tries to keep them from seeing the film). He also deliberately tries to avoid her out of loyalty to his best friend/her husband, which she interprets as him disliking her.
In the movie The Watcher, Keanu Reeves' character David Allen Griffin is a Stalker with a Crush. Not surprising, considering the title. Apparently the Foe Yay going on between him and Joel was so strong that he became obsessed with getting Joel to continue their Mind Games. He follows Joel all the way to Chicago, watches his every move (lamenting that Joel keeps going to the same terrible Vietnamese restaurant every night), sends him flowers and a card saying he missed him, kidnaps and tries to kill his female psychologist, and kidnaps him to try to get him to realize that they need each other. It's revealed later on that Joel's ex-lover was killed by David due to his being jealous that Joel was going to retire to be with her.
Obsessed is all about this trope; it features Ali Larter's character Lisa, er, pining over her boss Derek, going so far as to get into a fight with Derek's wife Sharon. The fight ends with Lisa dangling from a hole in the ceiling, about to plummet onto the glass table below her—Sharon tries to pull herback up, but Lisa attempts to drag her down as well, and ends up falling and being crushed by a broken chandelier.
There's a subtle hint of this with Eddie Brock in Spider-Man 3; he's always going on and on about how Gwen Stacy is "the girl I intend to marry" and tells her father that he's her boyfriend... and then, the first and only time we actually see them together, she reminds him that they've only ever had coffee once, in a fashion that indicates that she's really not that into him and that more than a bit of their relationship only exists in his own head.
Annie Wilkes in Misery, except she doesn't need to stalk — she gets home delivery!
Robin Williams' character in One Hour Photo has a crush on an entire family because they're so picture perfect. Using the information he's gotten from their photos, he fantasizes about visiting their house and being an Honorary Uncle. When he discovers that the husband has been having an affair he becomes enraged at him for squandering his "perfect" family and gets his revenge by catching him and his lover and forcing them to take sexually explicit photos, repeating the instructions his parents gave him as a child ("stop crying, you're supposed to be happy!").
Mad Love stars Peter Lorre as Dr. Gogol— a man obsessed enough with a beautiful actress to keep a wax dummy of her in his house to talk to. Slightly averted in that he knows she's happily married and tries to save her pianist husband's career when he loses his hands in a railway accident (he performs a successful transplant)— but he performs the surgery to endear himself to her, and when the husband start to think his hands have a mind of their own, Gogol has no problem trying to drive the husband crazier.
Batman: The Joker is this to Vicki. After seeing a picture of her he immediately develops feelings for her. The Joker even goes as far to kill everyone in a museum just so that he can talk to her. Near the end of the film, he manages to kidnap Vicki until Batman shows up to save her.
After she finds out Bruce is avoiding her, Vicki resorts to following him around, digging up files about his past, and spying on him to get to know him better.
Quite possibly Jackson Rippner in Red Eye. It's never explicitly stated but the character does seem a little fascinated by the girl he's been stalking ("When this is over, I may have to steal you.")
Confirmed by Word of God; Jackson did develop feelings for Lisa over the eight weeks he had to watch her. Not nice feelings, but feelings nevertheless.
In the commentary during the restroom scene, when Lisa revealed that she had been raped, Wes Craven notes, "He looks jealous." He sounded sort of creeped out as he said it. Let me repeat: Wes Craven was creeped out. That's Cillian Murphy for you.
In The Science of Sleep Stéphane does break into Stéphanie's house to steal something of hers to make it into a gift. She does catch him the second time and tell him to get out — this is put down to his lack of social understanding (thinking he was doing something nice for her). When she learns what his gift was ( making her childhood toy horse robotic enough to gallop - which she said she dreamt about as a child) she apologised for getting angry but does say that breaking into people's houses is wrong.
Used rather cleverly in He Loves Me... He Loves Me Not. The first half of the movie sets up that a girl named Angélique is the lover of a doctor and nearly commits suicide upon learning that he will not be leaving his wife to marry her. The second half reveals that this is all in her head - he only knew her vaguely because she house-sat for his neighbor, and it is also implied that she hit his wife with a motorcycle to cause her to miscarry as well as built a shrine to him out of garbage. While the girl is given medical help at the end, it is revealed that she was not taking her medication - instead using it to make a mosaic of the doctor.
The whole plot of The Crush starring Alicia Silverstone and Cary Elwes.
Used to a very creepy effect in Manon des Sources (Manon of the Spring). Ugolin, an ugly man in his 30s, spies on the teenage Manon as she is bathing. He then proceeds to spend days silently following her around as she herds goats, going so far as to fill her traps with game, but never allowing her to see him. The extent of his crush is revealed when he finds the bit of cloth she used to tie her hair back — he takes it home and sews it onto his naked chest.
This happens to all parties in the Love Triangle in Scott Pilgrim vs. The World. Knives was this to Scott, though it could be her way of showing affection. And when Scott broke up with her, she got worse. Then Scott followed Ramona around during the party. And Ramona admits that she did this to Gideon.
How the two main characters met in Dead Friend (aka The Ghost)...although it's treated as something sweet:
Ji-won: "How did we meet?" Boy: "When you were in school...I saw you crying in the rain. Because your father had died. I couldn't just walk by, so I bought you some hot noodles. (Smiles fondly) After that, you waited for me every night in an alley. Somehow you got my number and you kept calling. " Ji-won: "I did?"
Philippe from Une histoire sans importance (1980) turns into this after his rejection by Claude.
Louis Tully is this in the first Ghostbusters. He apparently sits just inside his apartment door all day, just waiting for Dana Barrett to walk by so he can come out and ask her on a date.
Janosz Poha in the sequel is even worse. At least Louis had a saving touch of geeky awkwardness about him; Janosz is actually creepy about it, especially when Vigo "helps" him.
Green Lantern: Hammond. He starts off with merely an infatuation, but by the time Carol gives him a hug and he smells her hair, it's gotten pretty twisted.
The 1981 movie The Fan is about an actress named Sally Ross who is being stalked by an obsessed fan named Douglas Breen. He starts with constant letters and requests for pictures and then moves on to murdering everyone she knows.
Knox Overstreet in Dead Poets Society when it comes to Chris, is a variation, but still disturbing. He shows up at her cheerleading practice wearing dark glasses though. He then grabs her boob at a party and then follows her to her school and rambles at her disturbing assumptions.