Osamu has eyes for Minae, the old widow that runs the restaurant him and his brothers frequent. She doesn't realise it and views him as a bumbling glutton.
Misuzu likes Wataru, but he has feelings for Natsuyo. This doesn't stop Misuzu from being obsessed with him to an unhealthy degree, even leaking his father's dirty secret to a magazine whe she gets the chance.
Xuan Nu loves Li Jing, who loves Bai Qian, who loved him until he cheated on her.
Su Jin loves Ye Hua, who thinks of her as family and loves Bai Qian.
Princess Silver: Rong Qi and Fu Chou are in love with Rong Le, who loves Wu You, while Hen Xiang and Ya Li are in love with Fu Chou.
Princess Agents: Yuwen Yue and Chu Qiao love each other. Yan Xun and Xiao Ce love Chu Qiao. Yuan Chun loves Yan Xun, who agrees to marry her then leaves her before the ceremony. And Wei Shu Ye loves Yuan Chun.
Lost Love in Times: Yuan Ling loves Qing Chen, who loves him too but who is determined not to accept him. Jin Hui loves Yuan Zhan, who loves Qing Chen. Mu Ke Sha loves Duo Xia, who loves Yuan Ling. Yin Cai Qian also loves Yuan Ling, but eventually switches her affections to Yuan Che.
The King's Woman: Jing Ke, Han Shen, and Ying Zheng are all in love with Gongsun Li. At first, she loves Jing Ke, but she eventually falls in love with Ying Zheng. And Ge Lan is in love with Jing Ke.
Ashes of Love: Kuang Lu loves Run Yu, who loves Jin Mi, who loves Xu Feng. And Sui He also loves Xu Feng.
He Xia loves Bai Ping Ting, but she doesn't return his feelings and falls in love with Chu Bei Jie. Later He Xia marries Yao Tian, who he doesn't love but who loves him.
Consort Zhang is Sima Hong's concubine, but she loves Chu Bei Jie. He loves Bai Ping Ting instead.
Lady Thirteen also falls in love with Chu Bei Jie, who's still in love with Bai Ping Ting.
Goodbye My Princess: Xiao Feng and Cheng Yin love each other. But Xiao Feng thinks Cheng Yin is in love with Zhao Se Se, and Gu Jian is in love with Xiao Feng. Mi Luo and Luo Xi both love Pei Zhao, who marries Luo Xi but doesn't love her. Adding to the confusion, Cheng Yin thinks Xiao Feng is in love with Xiao Wu... but thanks to Laser-Guided Amnesia he's forgotten Xiao Wu is the alias he used when he first met her.
Lysa Arryn only has a thing for Petyr Baelish, who only has a thing for Catelyn Stark (and her Generation Xerox daughter Sansa), while Catelyn only sees Petyr as a little brother.
Brienne of Tarth loves Renly Baratheon but his affections lie with Loras Tyrell who is crushed upon by Sansa and many other highborn girls. Later on, she develops feelings for Jaime Lannister and while he does reciprocate and they end up having sex, he leaves her afterwards because he still harbors love for his sister Cersei.
Orell declares his feelings for Ygritte, but she rejects him in favour of Jon.
Jorah's Wife Husbandry on Daenerys is not working in his favor...
Step by Step: Al Lambert was a tomboy during the early seasons and one of the earliest episodes—the one where Steve Urkel crash-landed in the Lamberts' yard—had her trying in vain to catch the eye of a good-looking sixth-grade classmate to take to the dance. Steve helps her to realize that the boy didn't want her (because she was too tomboyish) and there were others more worthy of her time. However, this is averted in later seasons because she grew up into a very attractive girl who has no problem attracting boys.
Early Buffy the Vampire Slayer is like this until somewhere in the middle of season 2. Oz is interested in Willow, who has a crush on Xander, who likes Buffy, who's in love with Angel (who proves the exception to the trope by loving her back, though his vampirism and his curse provide obstacles of their own). Then Willow falls for Oz, Xander and Cordelia hook up, etc.
Comes up again in season 5; Harmony is enamoured with Spike, who's obsessively infatuated with Buffy, who already has a boyfriend in Riley, who loves her but doesn't believe she loves him to the same degree. There's also Dawn's brief Precocious Crush on Xander and later on Spike, which are both (obviously) unrequited. And Drusilla comes back for an episode, hoping to rekindle her Unholy Matrimony with Spike, only for him to betray her and try to use her in a twisted Grand Romantic Gesture to prove his love for Buffy.
In Babylon 5, the Trope Namer, there's Marcus for Susan, Lennier for Delenn, Garibaldi for Talia, Zack for Lyta, and Corwin for Susan (at least on a crush scale).
Then again, the same show also had successful relationships: Sheridan and Delenn, Sinclair and Catherine Sakai note Though she did escape a very nasty fate due to Sinclair being written out; She was meant to be the one who was meant to be mentally hollowed out by the Shadows instead of Anna Sheridan, Garibaldi and Lise, and possibly G'Kar and Londo (that one's platonic). And its hinted Susan actually had feelings for Marcus but never admitted it (which only makes it more tragic).
In ER, Rocket Romano pines after Elizabeth Corday for a whopping seven years, from their first meeting until his death.
"The Ski Lodge" features the cruelest punchline of all these examples; after all the running around, Frasier is left to come to the painful realization that absolutely no one was interested in him. The Tag has the woman Frasier was after actually change her mind about him and knock on his door. After getting no answer, she leaves, disappointed. As soon as she's back in her own room, Frasier walks out of the kitchen and goes back into his room, oblivious to the fact that she was ever there.
On a more long-term basis, for the longest time Niles' crush on Daphne was firmly unrequited, long enough for him to finally give up on her and move on with someone else, just in time for Daphne to learn of his feelings and realize that she really was in love with him.
24's seventh season seems to have a pint-sized version of this going on: Janis likes Larry Moss, who likes Renee Walker, who likes Jack Bauer, who… probably likes Renee, or possibly only loves killing terrorists. Then season 8 shows that, yes, Jack does indeed like Renee.
On How I Met Your Mother Barney spent the entire fourth season secretly pining after Robin. Then, in the season finale, she says that she loves him back. Instantly, Barney's completely over his feelings for her and goes back to hitting on random bimbos. Then, when he finds out Robin lied about being in love with him, he goes right back to wanting her again. This all eventually leads to them doing a rapid-fire version of this trope.
Barney: Why are you so afraid of giving this a chance?
Robin: Because I'm scared of how much I like you!
Barney: Whoa, this is a bad idea.
Robin: Uch, you're right, it's a mistake.
Barney: Yes… No!
Robin: I love you.
Barney: Let's be friends.
Robin: Okay, friends then.
Barney: I love you.
Robin: Let's get married!
Barney: No, you're smothering me!
The Russell T Davies-era Doctor Who. Mickey loves Rose, but Rose loves the Doctor, who Rose's mother Jackie flirts with on their first meeting, but he won't allow himself to fall in love, he is later loved by Martha (who the Doctor rejects at every chance), was loved by Sarah Jane Smith, and had been (at least one side of him) loved by the school Matron Joan. Oh, and Jack loves everyone, except Donna. This is not at all the case in the classic series (even Sarah Jane's attraction for him is a Retcon), and becomes much less true in the Steven Moffat era. Although you have Rory's love for Amy (and Amy's ignorance of this) when they were young, and Amy's attraction to the Doctor (and his disinterest in her the knowledge that she's engaged). There is huge disagreement as to whether this trope applies at all between the Doctor and Clara due to the series continually zigzagging around it; the general agreement is that it was finally averted at the very end of Series 9 when both the Doctor and Clara ended up on the same page ... of course, just in time for her exit. Immediately thereafter, the trope tried to reassert itself as River Song, in the 2015 Christmas special, pretty much claimed that her attraction to the Doctor - despite the two being married - was one-sided.
The tradition continues in Torchwood. Tosh is in love with Owen, who is either not interested or too proud to give her a chance. Gwen loves her boyfriend, but she loves Jack even more. Jack loves Gwen too, but he is aware that she's taken. He is, in turn, casually involved with Ianto, who is pining for much more than that.
In Smallville, Clark with Lana in the first season. Chloe with Clark for the first half of the show, though she eventually got over it. Pete also had a secret crush on Chloe before he was Put on a Bus. Lex towards Chloe is hinted subtly (and less subtly in a deleted scene), Lionel is confirmed by Word of God to have a bit of this and a Villainous Crush, towards Chloe. Lionel to Martha too.
In Glee Ken falls for Emma who pines for Will who's married to Terri. Until Will finds out Terri lied about being pregnant and then falls for Emma although Ken is still out in the cold.
Mercedes likes Kurt, who likes Finn, who is both interested in Rachel (who likes him back) and dating Quinn, who is cheating on him with Puck, who is dating Santana, who also has little side-flings with Brittany.
Kartofsky → Kurt → Blaine → some random guy at the Gap
Artie has a fling with Brittany because he still likes Tina, who has moved on to Mike Chang.
Artie misses Brittany the second time they break up. He tries (unsuccessfully) to win her back). At the same time, Santana is in love with Brittany, but is dating Kartofsky, who also seems to have a thing for Sam.
Will likes Emma but makes out with Shelby, has a sleepover (strangely, a literal one) with April Rhodes, and is in the process of divorcing Terri. Emma likes Will too, but is tired of trying to make their relationship work… so she moves onto Carl the dentist. Sue also develops a one-episode crush on Will.
Rachel likes Finn who is dating (and eventually breaks up with Quinn), so Rachel moves onto Jesse while still having feelings for Finn who ultimately decides he wants to be with Rachel. And this happens twice.
Quinn dates Sam, cheats on Sam with Finn, and then Santana breaks Sam and Quinn up so she can date Sam. After Sam and Santana break up, Rachel tries (unsuccessfully) to ask him out.
Jacob Ben Israel likes Rachel, which never changes. Also, Puck's crush on Lauren goes unrequited for quite some time.
In Primeval, the main character Nick begins to fall for Claudia who is then erased from the time line and replaced with an alternate version called Jenny who Nick also falls for until he's shot. Likewise, Nick's ex-wife Helen tries to seduce him but fails and then tries on his best friend Stephen who leaves her after he ''finally'' realises the sort of person she is—and then sacrifices himself. Abby falls for Stephen at the beginning of the show's run but is discouraged when she learns he already has a girlfriend (who is not Helen). Of all the relationships in the show, only the Connor/Abby arc comes to something—and even that took two whole series and the better part of a third.
The Vampire Diaries: Damon loves Elena, she doesn't love him back. He loves Katherine, who also doesn't love him back, but instead loves Stefan. Who is in love with Elena. In 2x22 and 3x09 Katherine reveals she loved Damon too. And both times, she says it after saving Damon's life. Subverted in Season Four when Elena transitions and admits to Stefan that her feelings for Damon have been magnified. This causes a mutual break up.
The first few episodes seemed to offer a fairly predictable version of this, with Official Couple Jeff/Britta and Beta Couple Annie/Troy. But it eventually subverted this, in that after a while the characters decided to move on to other people instead of fawning over someone seemingly uninterested. There is still occasional Ship Tease between these pairings, but it's not a primary focus (and there's just as, if not more, Ship Tease between other pairings, such as Jeff/Annie).
In one episode, this trope is rather hilariously subverted, with Britta playing up her "unrequited love" for Jeff to the hilt in order to gain sympathy from the rest of the college (never mind that she was never anything more than briefly infatuated with him, if that). This backfires spectacularly when Jeff pretends to publicly confess his love, which she rejects, leading to everyone taking his side instead.
As of the season 4 finale of iCarly, Sam has fallen for Freddie who has fallen for Carly who could be harbouring her own feelings towards Freddie due to a breakup after he saved her life in an earlier episode eventually lead to them breaking up because of Freddie was unsure if Carly really loved him and not just because he saved her life. In the season 5 premiere, the sequel to the season 4 finale has Freddie kissing Sam and returning the feelings Sam has for him.
C-drama Holy Pearl (loosely based on Inuyasha) has this in spades. To begin: Mo Yin loves Rong Di who loves Xian Yue who loves Wen Tian. Wen Tian manages to buck the trend with Xian Yue's reincarnation Ding Yao, who loves him back. Until the very last episode, at which point it is played depressingly straight.
Bunheads. Truly loved Hubbell who loved Michelle until he dies while Michelle doesn't love anyone really, not even herself. Meanwhile Boo loves Charlie who's barely aware of her existence and all the girls except Boo are in lust with Godot who, again, is barely aware of them except for Boo with whom he's friends.
On The Big Bang Theory, Leonard started pining for his neighbor Penny the minute they meet. Penny thought of him as a good friend, and continued to date the Dumb Ass Jerk Jock type. Eventually, after a few false starts, they get together in season three… and then they break up because of The "I Love You" Stigma, specifically Penny not being ready to say the words yet. Then in season four Leonard gets a Romantic False Lead… er starts dating Pryia… and Penny begins to confront her feelings for Leonard, realizing she still cares about him and that he's a great guy, probably the most genuine man she's dated (and undoubtedly the smartest). And also still dating Pryia. It eventually becomes averted.
In Dracula (2013), Lucy is in love with Mina, who is engaged to Jonathan, whilst Lady Jayne fancies Grayson who is pining for Mina, the look-alike of his deceased wife.
In Shadowhunters, Maureen has a crush on Simon, who has a crush on Clary, who's in love with Jace.
El Chavo del ocho: with the adults; Doña Clotilde has a crush on Don Ramón and Don Ramón on Gloria. With the children; Chilindrina (Don Ramon’s daughter) has a crush on Chavo and Chavo on Patty (Gloria’s niece). The only requited and mutual crush is between Doña Florinda and Profesor Jirafales.
My So-Called Life: Oh God. Angela loves Jordan, Brian loves Angela, Angela's little sister crushes on Brian, Angela's friend Rayanne sleeps with Jordan at some point and there's hints Rayanne likes Angela, and it gets worse from there. None of them are happy.
All throughout The Adventures of Pete & Pete Big Pete and Ellen never seem to be interested in each other at the same time. Initially, Ellen seemed to have a crush on him, and would introduce herself as "Pete's girlfriend", causing him to say, "You're a girl, and you're a friend, but you're not a girlfriend." But whenever she appears to be interested in another guy, Pete would get jealous, and vice versa. They did have a kiss at the end of the episode "The Day of the Dot", but nothing came out of it.
Dark Desire: Esteban has had a crush on Alma from the day he met her. However, she still chose his brother Leonardo over him.
The Journey of Flower: Zi Xun is in love with Zi Hua, who's in love with Qian Gu. Dongfang Yu Qing, Xuan Lang and Qian Mo also fall in love with Qian Gu, who's in love with Zi Hua. Qing Shui is in love with Xuan Lang.
Ruyi's Royal Love in the Palace: Oooh boy... All of Hongli's concubines love him (or at least compete for his favour since they have no other options), while Hongli loves no one but himself. Yunche loves Yanwan, who leaves him to become one of Hongli's concubines. Li Yu loves Suoxin, who loves Jiang Yubin.
XO, Kitty: By the end of Season 1, Kitty develops feelings for Yuri. She even says that she feels like her heart is getting ripped out of her chest whenever Yuri talks to her girlfriend, Juliana. Meanwhile, Min-ho gets a crush on Kitty and Dae is still in love with Kitty.
Young Sheldon: In "A Second Prodigy and the Hottest Tips for Pouty Lips", Sheldon thinks this trope is in effect when Paige declares that she had a crush on him too. Of course, that was just Paige stringing Sheldon along to prank him.
