F.E.A.R. 2: Alma in regards to Becket. She develops romantic feelings for him and frequently does Attempted Rape on him. However he fights her off each time and this angers her. At the end of the game she does eventually manage to rape him and is pregnant with his child.
A mild example in inFAMOUS, which has the homicidal character Sasha, leader of the Reapers and briefly the Dragon to the Big Bad prior to the game. Throughout the game, she develops a one-sided crush on Cole. The Player can pursue this by following the Evil Side mission path, or ignore it by playing Good side missions, or ignoring this mission set entirely. Playing Good will see a developing hostility towards Cole as his Karma increases.(Though there are scripted story scenes in which she reveals her true nature, regardless of Karma) While the player must fight her regardless of Karmic path, it has a bigger impact if the love is unrequited. Not Good with Rejection comes into effect once the players learns that Cole is a younger version of Kessler whose timeline is irreparably altered due to Kessler's interference. This means that Sasha is in love with Cole, but is also flirting with him as payback towards Kessler, who tossed her aside.
Played with in Chapter 4 of Unchained Blades:Hector works up the courage to declare his love to Mari, but she tells him that she will never love him. He then goes mad (marked with Red Eyes, Take Warning) and schemes to use the wish of the Titan that they are in to force her to love her. However, it turns out that Mari said that she would not ever love him because she CAN'T: she is a doll turned girl who did not have emotions, and wants to make the wish to get them. And Hector; he was so overcome with the desire of his wish that he ended up having to be Unchained by Fang, after which he is very apologetic over what he tried to do.
The bosses in Gingiva will immediately attempt to kill you when you refuse their marriage proposals.
Swan, the Big Bad of Lollipop Chainsaw took Juliet rejecting him so badly that he started a Zombie Apocalypse to get his revenge on her and the rest of humanity. Even worse, she never really rejected him in the first place. Swan was just a creepy stalker who had never even spoken to Juliet once and simply took Juliet dating someone else as a "rejection."
Gladiatrix: Most love interests in the game will amiably accept the Lady's rejection of their advances. Braxton is a very strong exception to this, as is the headmaster of the magic academy, and the stable hand during the prologue.
Ensemble Stars!: What Izumi has for Makoto can only be described as a one-sided heavy crush. He actively seeks to be near him, gets upset when he thinks Makoto is avoiding him, hires people to take pictures of him, and when someone once made a joke about producer confessing to Makoto on the school's roof, he stated that if such thing had happened, he would've pushed both Producer and Makoto off the roof and then jump off himself. One of his cards is even named "If you get too close to Yuu-kun I won't forgive you!".
Jin Kisaragi from Blazblue is another male example, and dangerously skirt with Cute and Psycho. Any moment he's mentioned about his brother Ragna the Bloodedge, he drops all his cool exterior and goes Ho Yay to the max 'Oh brother...~' and expresses his 'love' by trying to kill him. Then there's the final boss Nu-13, who is usually robotic with everyone else, but if she meets Ragna, she also becomes a crazed lovestruck and tried to have him and when Ragna refused, she attempts to kill him. Then you realize that Nu is based on Ragna and Jin's sister. God, it sucks to be Ragna!
Cia in Hyrule Warriors is so obsessed with Link that she declares war on Hyrule to kill Zelda and take him for herself when jealous of his relationship with Zelda.
In Ib, Mary is obsessed with forming a friendship with Ib, displaying jealousy towards Garry and trying to ditch him a couple times, even at a point where it's clear he's in trouble and needs help. She tries to attack Ib when she thinks Ib will leave her. She chases after Ib and Garry with a palette knife. When she catches up to them she locks them in her toy box. If you anger her enough over the course of the game, she murders Garry. And in the ending "Welcome to the World of Guertena," Ib collapses in despair at seeing Garry go incurably insane and Mary decides the best solution is to keep Ib and Garry trapped in her world forever.
Depending on the ending you get, Maria/Mary in Silent Hill 2. It doesn't get much more Yandere than going One-Winged Angel and becoming the Final Boss because the target of your obsession rejects you.
Grand Theft Auto IV: During a conversation with Niko, Eddie Low states that he loved a woman but later found out she was a "whore". This is likely the same woman he refers to on both of his blogs while buying supplies at a hardware store, a female clerk tells him "have a nice day" as many clerks are supposed to. Eddie, without adequate social understanding, believes she has a crush on him, so he follows her home and asks to "nurse" her (suck on her breasts) and when she resists, Eddie kills her in anger. He appears for a second time in a dark alleyway in western Berchem and attempts to make small talk. Niko is taken aback by Low's strange and disturbing comments, including asking Niko if he enjoys being spanked. Niko sternly tells Eddie to "fuck off", and that his behavior is "not cool." An enraged Eddie launches into a tirade about how exactly he's tortured and killed children. For example, he says that he once kidnapped a quarterback, conducted anal rape, "strangled him into knots," and pulled out the intestines of another girl "just to see if he could feel anything. But he couldn't," Eddie states. This prompts Niko to respond with, "You should get laid or something." Eddie says that he already did; "a little jogger down by the water, but you know what, handsome, I got a hunger tonight that can't be sated, come here!" Low then takes out a knife and attacks Niko, who kills him in self-defense.
In Jak II: Renegade, the motivation behind Erol's attempt to run down Jak is out of envy towards losing both the big race and Keira. His envy seems to have corrupted him, as in the next game, he outright tries to destroy the world... all for losing one girl.
Eddie Gluskin of Outlast has a misleadingly kind personality; he is, by and large, very charming, though upon being rejected he can become violent and insulting. He is obsessed with the idea of his "perfect bride," to the point where he mutilates people he deems mentally acceptable to make them physically acceptable as well. He appears to be only interested in taking men and removing and adding parts to create a woman by removing the penis, testicles, and excess body hair and adding breasts. His charming personality often slips when he is rejected, and he teeters dangerously between complimenting his "bride's" appearance and personality and insulting them, often using violent slurs.
In Sly Cooper: Thieves in Time, Penelope becomes a yandere obsessed with Bentley, but it's clear she's only using him for his skills to accumulate vast wealth, which he would rather use to aid his True Companions Sly and Murray. When he learns about hertruenature, he's heartbroken, but when he catches her trying to kill Sly, he has enough and dumps her. She does not take this well, with her attacking Bentley out of rage for their break-up, and the (aborted) Sequel Hook has her stalk him with postcards, showing she's out for revenge.
In the World of Warcraft short "Warbringers: Azshara", we see how Queen Azshara was approached by the Old God N'zoth with a Deal with the Devil. He would save her life from drowning if she would serve him. She initially tells the God of the Deep no. N'zoth is outraged by a mere mortal denying him and would have killed her himself had she not convinced him to sweeten the deal before accepting.