Haruhi, whose obliviousness to other people's feelings towards her has led to many accidental "Just Friends" speeches, usually when the person with a crush on her was about to give a love confession. Made doubly amusing by the fact that these appear to be about the ONLY feelings the normally perceptive Haruhi is oblivious to.
Tamaki takes this trope to its logical extreme. Although capable of being even more perceptive regarding the feelings of others than Haruhi is, he is oblivious to his own feelings towards Haruhi and thinks that his constant fawning over her can only mean that he thinks of her as a daughter.
Kouji Kabuto from Mazinger Z has absolutely no idea when a girl is interested in him.
Tetsuya Tsurugi from Great Mazinger is even worse, completely frustrating Jun Hono, who keeps sending him signals as he keeps misunderstanding them.
Sakura of Card Captor Sakura, who somehow missed the very obvious affections of her lesbian best friend and constantly blushing rival until one of them explicitly said that they love her in that way at the end of the series.
Also worth noting: aforementioned best friend actually does say she loves her that way quite early (in the manga), but it flies over her head completely.
Neon Genesis Evangelion includes a traditional take on this trope with Shinji and Asuka. Asuka is (according to Word of God) in love with Shinji and often flirts with him (showing him her cleavage before asking him if he believes that her breasts would grow if someone applied heat, looking for excuses to kiss him...). But since she is a traumatized, insecure and frightened kid that constantly pushes everyone away, and Shinji is a shy, insecure kid and she pushes him away constantly, he can't believe that she would be interested in him. In turn his obliviousness causes her to believe that HE is not interested in her, so she gets angry and continues pushing him away. (The last scene of End of Evangelion hints that maybe they may finally break the vicious cycle.)
Gray is very confused by Juvia's behaviour towards him. By the Grand Magic Games he has realized her feelings, but unfortunately, he tells her that he doesn't love her and is annoyed by her attentions. Yet he becomes jealous and possessive when someone flirts with her, especially his rival in Ice Magic, so he may be simply be in deep denial.
Gajeel is nearly as bad. In later chapters, Levi has moved from being an Implied Love Interest to blatantly having a crush. While Gajeel is noticeably more protective of her than anyone else, he still doesn't get it leading to normally the shy and reserved Levi to act more Tsundere-ish around him.
Kasumi seems totally unaware that Dr. Tofu is totally infatuated with her in Ranma ˝. Although given that Dr. Tofu basically flips out when he so much as hears Kasumi's voice, has been doing this at least since she hit puberty, and neither Ranma nor Akane want to tell her why the good doctor does so, it's quite plausible that she sincerely doesn't know what the deal is.
The titular character never actually picked up on Hyuuga Hinata's having a massive crush on him until she told him in Chapter 437despite everyone else seeing it; rather, he thought she was just being Hinata. When he actually found out after she confessed, he was very surprised.
Also deconstructed a bit. Naruto wasn't raised by a loving family and was something of a pariah. He does feel love and tries and show it, but few times have people shown him affection so the idea of someone loving him like that would come as a shock to him.
Sakura with Naruto also. Painfully. Sakura always knew Naruto had a crush on her or was attracted to her at the very least, but assumed that's all it was. When she realized Naruto was actually in love with her by Sai and that his feelings were serious, she was rather surprised and guilty.
Kakashi's old teammate, Rin, didn't realize Obito was in love with her. Kakashi told her after he died (or at least they thought he was dead). Rin didn't take it well, especially considering that like Sakura's unrequited crush on Sasuke, she had unrequited feelings for Kakashi.
Train from Black Cat, being the Chaste Hero he is, is very oblivious of a lot of character's feelings for him. Though he's especially this way with Creed, who is unbelievably outright about his scary obsessive love for him. In the manga, after all these years, Train is shown to still be incapable of understanding what possible reason Creed would have for killing Saya. There's even a scene where Creed tells Train that he would at least want to have Train by his side even as a dead body rather than have Saya have him. When other characters are creeped out by this, Train dismisses it by telling them to ignore him, and that Creed is simply being selfish and weird. Missing the point, no?
The titular Hayate the Combat Butler is very oblivious to pretty much all the characters' love for him, with the exception of Ayumu, who he seems to be treating normally after she confesses to him and Kotetsu, because he doesn't swing that way. Isumi is completely oblivious to Wataru's crush on her, while Wataru is oblivious on Saki's crush on him, but is slightly aware of Sonia's crush on him after she kisses him as part of the deal to save Saki from the kidnappers.
Negi is utterly oblivious that a number of his students are in love with him, only picking up on it when they tell him to his face. Somewhat justified by the fact that he's too young to know what's going on, and several of his students (especially Chisame) point out just how blind he is to anything involving romance and note that this is going to lead to a lot of trouble in the future.
In chapter 269, we see that Negi apparently got it from his mother Arika, who for all her intelligence was still unable to tell Nagi had feelings for her until he flat-out stated it to her.
Negi's friend/rival, Kotarou, has it just as bad as him when it comes to his surrogate sister Natsumi's blatant feelings for him.
Konoka seems to be clueless about Setsuna's feelings for her, but for about the entire series there seemed to be somedispute over whether Konoka is truly completely oblivious, a downright sadistic tease, or making subtle overtures 'Set-chan' is too dense to realise are intentional, although it's more likely the third suggestion.
Setsuna is herself oblivious to love, and constantly insists (to herself) that having romantic feelings for Konoka would be wrong- and that Konoka would never be interested in her like that anyway- it seems likely that it's the latter. Konoka canonically states that she really, really wants to have the same close, easy relationship with Setsuna they shared during childhood, and does many things to achieve this end. This is so bad that Negi can see the attraction between them, despite normally being utterly clueless in matters of love.
Subverted when it seems that Umi is unaware of Ascot the Summoner's feelings for her. It becomes apparent that she knows, she'd just rather stay friends and not talk about it.
Hikaru in the manga. Not only does Hikaru totally miss the fact that Fuu and Ferio like each other (Even after seeing Ferio kiss Fuu's hand, causing Fuu to blush furiously), her reaction to Lantis asking her to marry him is to say that she wants to spend the rest of her life with the ones she loves - and defines 'the ones she loves' as just about every named character in Cephiro that is still alive.
Otani from Lovely Complex. Not only is he initially completely oblivious to Koizumi being head over heels in love with him, even writing off an outright declaration of love from her as a joke, but he also doesn't realize that his childhood friend Mimi is also madly in love with him, which makes Koizumi express sympathy for her own romantic rival for having to deal with Otani's denseness ever since childhood.
Himawari appears very oblivious to Watanuki's obvious affection for her, turning it up when he gets more direct. This turns out to most likely be a Subversion: she chooses to pretend obliviousness in the hopes of protecting him from the supernatural bad luck that hovers around her and afflicts those she becomes close to.
Watanuki, meanwhile, utterly fails to catch on to the fact that Doumeki keeps on hanging around because of him, assuming instead that Doumeki is his rival for Himawari's affection and/or just generally trying to annoy him.
Watanuki also never realizes Kohane had developed feelings for him until she's already on her way to getting married, when her soon-to-be-husband Doumeki points it out.
Kyon from Haruhi Suzumiya, despite being told several times by Koizumi (who openly and exasperatedly states that he can't believe Kyon still doesn't get it) about his importance to Haruhi, despite her hitting him with clues as subtle as a brick, despite him kissing her in closed space being the only thing that makes her want to return to the real world, still insists he has absolutely no idea why Haruhi gets so upset every time he acts too familiar with other girls. Partly on account that Kyon is an Unreliable Narrator, and partly because he's very good at putting walls up in his mind around things he doesn't want to think about.
With regards to Haruhi, Kyon transitions to Selective Obliviousness fairly quickly. He remains clueless long after Everyone Can See It so it still fits, despite being told point blank he was "chosen" by Haruhi four times. And he was pretty much the only one she talked to at all. And that he was the only one she kept when she started rewriting reality. And that is just the first book. Haruhi doesn't do subtle.
It's later revealed that Kyon also had this with regards to Sasaki, his "close" friend from middle school and the origin of his reputation of liking weird girls.
Haruhi herself also seems to have this. She is oblivious to Kozumi's feelings for her. And Kyon's later on when he starts to return her feelings. To be fair, they are both trying to hide how they feel from her, but for different reasons.
Wilhelm Schultz in Allison and Lillia manages to remain completely unaware of his childhood friend Allison's feelings for him, in spite of his Hyper Awareness and Photographic Memory. Until she pins him down and forces him to kiss/marry her, anyway. In the second half, his daughter Lillia can also be like this, though it's exacerbated by the fact that the people around her help to keep it that way.
Hikari from Special A is utterly unable to separate "rival" and "lover" in her mind, and despite the most obvious hints from Kei (even a kiss and Kei attempting to get a date with her), she continues to be blindly ignorant of this. Yet everyone else around them seems to have caught on.
Kaze no Stigma neatly subverts this. Kazuma almost certainly knows Ayano likes him and is willing to go on missions with her if paid by her father, who is trying to invoke Bodyguard Crush on him.
In the Girls LoveManga, Girl Friends, Akko is completely oblivious to Mari's affections despite twice being kissed by her, and hearing what should have been a love declaration. Mari is likewise oblivious to Akko's affections although Mari hasn't seen as much evidence of those feelings.
In the Hen manga, popular Chizuru couldn't have been more obvious with her crush on Yamada, what with her blushing, sweating, stammering and even outright telling Yamada that she loves her. Yamada keeps treating Chizuru as a friend (albeit a weird one), even after Chizuru's very transparent attempt to steal a kiss from her—that is, until Chizuru practically explodes in a dramatic public love confession.
For the majority of Full Metal Panic!, Sousuke remains completely oblivious to the romantic feelings that various people hold towards him, utterly misinterpreting or blowing off several all-out Love Confessions. There are some indications that at least some of his obliviousness is a purposeful, if perhaps subconscious, means of avoiding the issue - he's at his most clueless when it comes to the incredibly aggressive and persistent advances of his commanding officer, Tessa - but it's also clear that a lot of it comes from the fact that he simply doesn't understand love at all, since he has never been in love before and has nothing to compare it to. It takes him a long time to recognize his growing feelings for Kaname for what they are; when he and Kurz discuss the subject in the novels and Kurz tells him it's love, Sousuke doesn't believe him, as love is supposed to be happy and he is miserable.
In the World War IIGirls Love manga Kurogane Pukapuka Tai, Commander Kuki acts wholly obliviously to the wholly obvious attraction of her XO, Mamiya; even when she's told about it, she responds, "Don't be ridiculous! It is not possible between women!" She gets really flustered when women make advances on her, though, suggesting that the obliviousness may be denial rather than cluelessness...at least sometimes.
Pokémon Special: Red. Even by the end of the Emerald arc he remains blissfully unaware that Yellow and Misty see him as more than a "friend" at times (though the end of the GSC arc indicates that this is intentional obliviousness on his part, as dealing with romance makes him very uncomfortable).
Keitaro in Love Hina has a really hard time figuring out that the girls have feelings for him.
In his defense, they spend the entire manga beforehand beating him up for being an Accidental Pervert. It'd be a tough pill to swallow for him to think that they liked him as anything more than a friend.
Kyohei and Sunako from The Wallflower absolutely refuse to even entertain the thought that they're in love with each other- Sunako going as far as to say 'Love is an illusion' and Kyohei using the excuse that he 'loves her food'- and this is after they've kissed twice, saved each other countless times and had the entire cast calling them out on their UST and feelings - so much that at this point of the manga everyone is convinced they are in love/together. EVERYONE. EXCEPT. THEIR STUPID SELVES.
Suetake from Doki Doki School Hours absolutely fails to recognize that his (male) classmate Kudo has a major crush on him. Of course, Suetake is quite dumb, but Kudo doesn't really keep it a secret, so everybody else knows.
Ami in Toradora! is very very transparent with how she feels about Ryuji, dropping incredibly obvious hints ("I would be your equal in a relationship") but since she never actually says anything outright, Ryuji is oblivious. So is the rest of the cast...
In Saki, Nodoka forms quite a crush on Saki, to the point that it has a negative influence on her Mahjong-playing abilities. Most everyone in the mahjong club seems to realize this—except for Saki herself.
Shunsuke from Yuria 100 Shiki has no clue that Yuria likes him despite how hard she tries to take care of him, not to mention her constant attempts to have sex with him.
Boa Hancock is (extremely obviously) in love with main protagonist Monkey D. Luffy, yet is too shy to say it outright. He has no idea whatsoever.
Considering he tells her after the timeskip that he won't marry her he probably knows but isn't interested.
We also have Camie, who furiously blushed and stammered when Shakky asked if she was Hatchan's lover. Hatchan himself barely reacts to the question. Or perhaps he does know but doesn't want to embarrass/encourage her.
In Ayashi no Ceres, Aya becomes flustered when Tooya kisses her, she falls asleep in his arms, and STILL his stoicism prevails. He does realize his feelings for her a couple of episodes later, but it takes longer—and is played straighter—in the manga.
In Kämpfer, Natsuru is probably one of THE most oblivious people when it comes to love. Only loves a Satellite Love Interest and he still has three people going crazy for him. He STILL doesn't even know about it.
In Simoun, Aer (Aaeru?) falls under this. At the start, she has no idea why anyone would want to kiss someone else if they weren't about to pilot a Simoun.
Nanako Yamamoto, a teacher at Hanamaru Kindergarten is described as having a world-record level ability for not noticing when men are interested in her. This actually seems to be a family trait, as her younger sister Mayumi exhibits the same trait when a man shows interest in her. Oddly enough, the Yamamoto sisters can each spot the other's respective suitors, but not their own.
Goku probably takes the cake. Chi-Chi develops a crush on him right after meeting him, and he fails to pick up on it, and when she asks if he'll marry her he thinks that marriage is food. As of Dragon Ball Z, however, it's clear he loves his wife, although he still has a funny way of showing it.
Saiyans are not as well connected to emotions as humans are. That and Goku was raised by his adoptive grandfather in the wilderness for his youth with his first friend being Bulma, whom acted like an older sister of sorts.
Subverted by his son Gohan. For a while, it looks like he's oblivious to Videl's crush on him, but it soon becomes apparent that he also has feelings for her and is just scared to acknowledge them (the issue with Buu was probably a factor also). This changes once his mystic training is through.
Jaden in the dub with Alexis, because there are some added hints of her feelings for him in the dub that make him a complete dunce for not picking up on them, most notably when she tells him what a marriage is (because he didn't know), she says "it means friendship, at least for now big guy." Note in the original she just called him an idiot.
In the manga, Ryo falls into this, although in fairness, it's regarding love for another person. After he consoles Asuka after her loss to David, Misawa gets somewhat jealous, vowing to face him "as a duelist and as a man". Later on, after Asuka and Misawa's team battle, when Fubuki declares that his sister is off limits to Misawa, Ryo doesn't understand what he means, and Fubuki is irritated that he is unaware of Misawa's obvious crush.
Italy from Axis Powers Hetalia is this in the Buon San Valentino comics. He simply thinks that Germany has been extra nice to him and doesn't realize that (from Germany's point of view) they've actually been going on dates. Nor does he realize that the reason Germany got upset when he saw him flirting with some girls is because he was jealous.
Spain probably counts too, seeing how he doesn't seem to realize the full extent/implications of Romano's Tsundereness toward him or that Romano didn't give a wholly negative answer to his marriage proposal.
One of the main foundations School Rumble is built upon. Tenma is too busy mooning over Karasuma to notice that Harima is mooning over her, and Harima is too busy mooning over Tenma to notice that Eri and Yakumo are mooning over him. (Not to mention that Karasuma is too busy mooning over curry to notice Tenma..... not that he cares anyway.) Hilarity and misunderstandings ensue, of course.
Kyoko from Skip Beat!, especially toward Ren. Justified because after Sho dumped her she gave up love and killed that area of her brain, vowing revenge.
Seiji in Midori no Hibi. Dear God, Seiji. He ends up with three (four if you count his neighbor's daughter) women and a guy lusting after him, and is only aware of one because she says so all the time. Another goes through a painfully transparent I Have This Friend confession to him and he still doesn't get who she's talking about until she's halfway through. And the justification for this? Because at 17, he's never had a girlfriend, and so is incapable of picking up the incredibly obvious signals.
In Aoi Hana, Akira doesn't realize that her infinite kindness toward her childhood friend Fumi causes the latter's feelings for her to resurface. That is, until Fumi finally confesses to her.
Kousaka spends most of the first volume of Genshiken completely oblivious to the fact that Kasukabe has a big crush on him, even though Sasahara (and really, the reader until Kousaka mentions this) assumed she was his girlfriend just because of how she acted around him. It's especially humorous in that Kousaka actually likes her himself, but the idea that she felt the same way simply did not occur to him. Madarme's sarcastic suggestion that Kousaka just kiss her and get the whole Will They or Won't They? subplot over with was genuinely the first time he had any idea she'd actually go along with such a proposal.
Yuuji from Shakugan no Shana is the resident Chick Magnet. He's also incredibly good at convincing himself that no girl could possibly find him that interesting and every time he gets suspicious about Shana and/or Kazumi being in love with him, he just shrugs it off as his imagination.
Moritaka of Bakuman。 initially assumes his feelings for Miho are unrequited, and only realizes that this is not the case after he confesses to her and promises to marry her once they achieve their dreams. It's later revealed that she has been in love with him since the fourth grade, and this comes as a surprise to him.
Heiji is apparently utterly incapable of realizing his feelings for Kazuha or vice versa; even going so far as to believe the jealousy he felt when she flirted with a magician was just a leader's concern for his follower. Ran is even worse, despite unknowingly returning Shinichi's feelings. But Satou has them all beat; she has never once twigged to the fact that Takagi, Shiratori, and every other single man in her department find (or used to find) her attractive, often leading to humorous misunderstandings. (Especially when a mischievous Yumi shamelessly takes advantage of that cluelessness to prank the rest of the department.)
Satou's is explainable as Selective Obliviousness, in her case with full knowledge and totally on purpose, out of her fear of inevitably losing every person she loves in the worst way possible (beginning with the death of her father and reinforced through the demise of former-bomb-squad Matsuda Jinpei). Takagi himself has a little bit of this, because of what happened to Wataru Date, but it's only affected him on the anniversary of the event.
Sonoko's boyfriend Makoto also seems to have a hard time picking up on her "subtle" hints—in the Valentine's Day episode where she went to a resort with Kogoro's family to make a chocolate heart for (she told Makoto) "the person she cared for most," Makoto showed up to see who this person was and if he was a suitable companion for her. This turned out to be a good thing, as he arrived just in time to help KO two murderers who got the drop on everyone else. When he asked who it was and Sonoko pointed at him, he turned around to look behind him. Granted, Makoto is truly NOT good with people.
Miu from Kenichi: The Mightiest Disciple has a bad case of this. Kenichi has it worse. He's so used to that idea that he's a loser that he can't even comprehend that girls will so much as LOOK at him, let alone have feelings for him. So when anyone besides Miu acts fondly towards him, he seems to shrug it off as them just being nice to him.
Bleach: Subverted by Orihime who has been in love with Ichigo for years but doesn't try to make him aware of it, and her only confession (to an unconscious Ichigo) was about gratitude and goodbye not about wanting him to return her feelings. The author occasionally shows us how she views him (more charming than he really is) but only for comedy as he's stated he doesn't intend writing romance. When he finally addresses it in the final arc, Orihime is tricked by Urahara into wearing a revealing dress to make Ichigo notice, it's again played for comedy to lynch a flustered Ichigo for saying the wrong thing and a smug Urahara for being such a pervert, but ultimately to ease the mood of the characters who have just discovered Uryuu's joined the enemy's side.
Ennis from Baccano!. Firo reports that she didn't quite catch on for fifty years.
Kumiko from Gokusen is incredibly clueless about Shin's feelings for her, even as his extremely unsubtle friends try to help him out. Even the teachers were aware of Shin's crush on her before she did.
In the Live-Action Adaptation, Kumiko is completely oblivious to the male gym teachers crush on her through all three series. Too distracted by the guy of the season to notice.
Fuyuki Hinata of Keroro Gunsou is totally oblivious to the crush MomokaNishizawa has on him. Much to her endless frustration. It has been hinted, though, that Fuyuki is aware of Momoka's crush on him, and actually secretly returns her feelings.
He does get to even higher levels of denseness in Season 2, earning him the Fan Nickname "Neutron Star Ichika".
Hilshire from Gunslinger Girl is this, starting with Maria Machiavelli's hints that they should work out their relationship and going all the way up to obliviously ruining the atmosphere Triela made with a candlelit dinner. Considering her cyborg nature, and how much of that affection may be conditioning, which she admits she has difficulty telling apart (until a more recent chapter, she gets a Love Epiphany and indeed realises that her feelings for Hilshire are genuine), it's understandable. However, Hilshire still remains oblivious even to the increased affection she shows him after said epiphany, although the fact he was asleep (due to the painkiller from hastily administered field medicine) when it came to her and when she kissed him, it's also somewhat understandable.
Not to mention the fact that Triela is underage , and the survivor of a Snuff movie ring, that had her raped and tortured to the brink of death. One suspects that Hilshire ignoring her overtures is deliberate, and possibly the more considerate course he may take.
Guts from Berserk never really bothered to realize that Casca wanted him to stay with the Hawks - not solely because Griffith was so dependent on Guts as chief member of the Hawks - because she was falling in love with him. And the fact that he was so convinced that she was in love with Griffith even though he himself had a growing attraction to Casca at the time but refused to acknowledge their relationship as anything other than "friends" and wished the both of them happiness after he was gone didn't help.
He also completely and utterly fails to notice how obsessed Griffith is with him, to the point of assuming that his utterly crushed stance when Guts is leaving has to do with Griffith being unable to deal with being defeated. Good job, Guts.
Van of GUN×SWORD is blithely unaware of the romantic feelings at least two of the three women in his harem have for him. (He MIGHT have some idea about the third, but it's hard to tell.)
In Magical X Miracle, while Merleawe has at least some inkling of the crushes Vaith and Fern have on her, others are a bit more blind. For example, Yue doesn't get it. He didn't get it with the flirting. He didn't get it with the subtle attempt at a love confession, forcing Lenolora to lay it out for him, word by word, very explicitly, in front of all his peers and higher-ups. And then he turned seventeen shades of pink and was temporarily unable to form a coherent sentence. Of course, being a Kuudere probably doesn't help with the ability to recognize love.
In Tiger & Bunny, Kotetsu is completely oblivious to Karina's increasingly obvious crush on him. Not even Karina's giddy declaration that she'll cherish a towel he gave her forever seems to have clued him in. Word of God says he's always this oblivious when it comes to women's advances.
Saya from Blood-C is a rare female example, and one of the most extreme; at least two guys (Itsuki and Tokizane) are blatantly interested in her, but she manages to remain completely clueless. Subverted: Tokizane was faking it. Itsuki plays it straighter, though he fell for her later... and then he died.
Subverted in Mawaru-Penguindrum, since Tabuki wasn't that oblivious in the end. He was in love with Momoka, a girl who died many years ago.
Keiichi of Higurashi no Naku Koro ni was completely unaware of Mion's true personality, let alone her huge crush on him. His ignorance is revealed to be the trigger (he gives a doll he won to Rena, instead of Mion) for the bloodiest murders in the series.
In Iris Zero, Toru is oblivious to Sasamori's growing feelings for him. Though in chapter 27, Asahi calls Toru out on pretending to not notice Sasamori's feelings. Toru is only pretending to be oblivious because he is afraid of upsetting the uneasy balance in his newfound circle of friends.
He didn't seem shocked when she (eventually) plucked up the courage to ask him on a date, nor by the fact that she kissed him, and when C.C directly brought up the subject of their relationship he was unsure of how he felt, but didn't react with the surprise or denial one might expect for this trope. Add to this the fact that he's normally very good at understanding and predicting other people, and it seems likely that he was aware of how Shirley felt, and chose to stay Just Friends due to his own ambiguouslove for his sister, and later because he was preoccupied with running a terrorist/freedom fighter network.
Ryuuichi from Gakuen Babysitters is unfamiliar with how love is supposed to feel since he's never had a crush. As such, he's unaware of the feelings of romantic attraction that Ushimaru and Inomata feel toward him, which he ignited due to inadvertently using social cues that people who are aware of love would recognize as implications.
Arata of Amawakuni from Arata Kangatari is clueless to Kotoha's obvious affections.
Ran and Julia from Strawberry Shake Sweet spend a good deal of the manga like this: first by failing to notice their own feelings, then by practically refusing to acknowledge that said feelings are mutual. Hilarity Ensues.
Haruyuki Arita of Accel World has spent so much time as the Butt Monkey of various bullies that he fails to catch on to the feelings Kuroyukihime has for him. He even unknowingly shoots down a subtle confession because of this. After Kuroyukihime flat out confesses, the main problem becomes Haru's having a hard time reciprocating because of his own self-esteem issues.
Kuroyukihime herself is an example, as she expresses intense jealousy towards Haru's childhood friend Chiyu but is slow to realize it is jealousy.
Fai in Tsubasa Reservoir Chronicle doesn't seem to get how much Kurogane cares about him, even going so far as assuming that he hates him, and only wises up when Kurogane saves his life by making him a vampire and agreeing to become his food source for the rest of his life. Then he violently tries to retcon this by being a massive passive-aggressive dick. It doesn't work.
He snaps out of it and accepts it when Kurogane cuts off his own arm to save him in Celes and everything gets better from there.
Tamako of Tamako Market doesn't know she has already became the crush of both Mochizou and Midori, thinking they're just friends. The latter two actually got into a fight on Love Confession in episode 5.
Yuma Tsukumo from Yu-Gi-Oh! ZEXAL has Kotori, Cathy, and Anna all in love with him, but he somehow doesn't notice. In the final episode, Kotori confesses to him. He's incredibly shocked, but reciprocates.
Astral: Observation #11: Seems like Yuma still doesn't understand women's feelings.
Kotoura-san has a strange case: Manabe loves Haruka, and Haruka knows it. Haruka loves Manabe as well, but he doesn't notice it. This is exactly why his Childhood Friend Hiyori became his Hopeless Suitor—despite multiple hints that she's been attracted to him for years, he never seems to realize that she fell for him. This was lampshaded in the first chapter of manga, when Haruka, at the time still on a Jerkass Façade and hence quite snarky, calls him a "flag crusher."
Boku wa Tomodachi ga Sukunai has Kodaka, who manages to ignore the very blatant crushes of least six girls. Despite several of them outright telling him that they're into him, he just doesn't get it. Except that he does, and plays dumb to save their feelings. There's no way for him to pick one girl without ruining the friendships he has with the others, so he plays off their advances as best he can.
Chizu from Kimi ni Todoke to a crazy degree. She doesn't realise that Kazehaya likes Sawako even when it becomes cringe-makingly obvious, and poor Ryu has to confess to her twice, on different occasions, before she actually realises that he doesn't mean it platonically. Even without the confessions, there are times when a more observant person would have easily put two and two together.
Seira Mimori give him a fair run for his money: she can see feelings for others just fine, but when Sawatari fell in love with her and started courting her she just chalked it up to him being a Cloud Cuckoo Lander and Meimi (his previous love interest) finally being with Asuka jr., at least until he made her a barely veiled love declaration. She's also oblivious to her possibly loving him back, but, given she's a nun, it's just as likely she's actively suppressing them.
The hero Takeo from Ore Monogatari is rather dense when it comes to reading other people, so it requires his best friend to basically tell him that there's a girl that likes him for Takeo to really get it.
Eren in Attack on Titan is unaware of Mikasa's blatant romantic feelings towards him, instead being annoyed at her protectiveness. The implication is that this is a side effect of his Determinator status; all he can focus on is killing Titans. Mikasa is either an innocent to be protected or an ally to help kill them, just like everyone else. He's also unaware of Annie's feelings towards him, though in fairness she's much more subtle than Mikasa.
In Tonari no Kashiwagi-san Kotone asked Yuuto what date he was on that Tina asked him about, not realising she was referring to the Double Date Yuuto and Kotone herself went on with Sayaka and Kazuki. This is fairly typical for her.
In Koe No Katachi, Ishida is consistently oblivious to the female attraction towards him. When he was in grade six, it was due to his immaturity that he didn't realize Ueno was crushing on him. And in the present day, both Ueno and Shouko have feelings towards him. It's understandable why Ishida is igorant of Ueno's continued crush on him due to the fact he can't stand her. But for Shouko, it's likely from his own self-loathing that prevents him from realizing it.
Gundam Build Fighters has Reiji. Having a girl follow you back to your home world and you still don't know why?
Ditto with the sequel and Sekai when a female rival makes him a bento.
Peanuts: Charlie Brown and Marcie. He's understandably intimidated by Peppermint Patty's overtures, but has yet to notice Marcie.
Let's not forget Charlie and the Little Red-Headed Girl, who probably doesn't even know he exists.
Charlie Brown does figure out that Marcie likes him, but not until she (very bluntly) tells him so. His self-esteem is so low, he can't really believe that any girl can be interested in him, even Peppermint Patty.
Rampant throughout the post-Zero HourLegion of Super-Heroes comics, and probably at least some of the other versions as well. XS in particular is known for developing intense crushes on characters like M'Onel and Cosmic Boy, both of whom are entirely oblivious; meanwhile, XS herself spends a while being completely ignorant of the fact that Dyrk Magz has a crush on her. Eventually she catches on, but they get just about enough time for one date before Dyrk gets Demoted to Extra and then wiped from continuity completely.
Calvin and Susie Derkins from Calvin and Hobbes. Word of Godsays that Calvin and Susie have a mutual crush on each other. Calvin, apparently, either doesn't know about it or doesn't know how to deal with it, so he does his best to gross out and anger Susie, who then always gets mad at him.
Arguably, this may apply with Susie as well. Susie generally is contemptuous of Calvin, ignores him, and associates with him only when she has to, but at the same time, perhaps like Calvin, doesn't know how to handle her feelings towards him.
Strangely enough, in the strip it's Hobbes (Calvin's alter ego?) who is attracted to Susie and is always convincing Calvin to go play with her.
"...So what happened to the mandibles of death, you sissy furball?!?"
"I was beguiled by her feminine charms. Yow. Go soak your head."
Most likely Calvin just projects his feelings onto his imaginary friend as a way of dealing with them.
Though Hobbes also sometimes teases Calvin by suggesting he and Susie like each other; assuming he is real, it's possible he's just acting infatuated to get under Calvin's skin.
Despite being able to sense the emotions of others, Teen Titans' Raven seems quite oblivious to Beast Boy's feelings for her.
The Soviet version of Superman is quite oblivious to Wonder Woman's feelings for him in Superman: Red Son, and it comes back to haunt him later on.
It is an all female island of rape victims with a "no boys allowed" policy. It could be he doesn't think her kind would ever have affection for a man.
In the newspaper comic strip Curtis, the titular character is too busy crushing on Michelle (who most definitely does not reciprocate) to realize that his good friend Chutney is head-over-heels in love with him. Once or twice he does wonder "Could it be that Michelle doesn't like me and that Chutney does?" but always writes the possibility off in the end.
In spite - or maybe because - the fact that he's possibly the biggest Chick Magnet in the DCU, Nightwing is at times utterly unaware that the girl he's having friendly banter with would like their relationship to go past the Just FriendsWill They or Won't They? stage. It might just be professionalism on his part, since practically every single superheroine (and a few of it's villainesses) in the DCU has expressed interest in him at some point. He normally seems at least embarrassed by the sometimes very blatant advances some have made towards him.
In Alex + Ada, it is made very clear that Isabel likes Alex, but the guy is too busy complaining about his ex to notice when she tries to ask him out, and afterwards, he gets too busy to really care, and outright ignores her calls.
In the My Little Pony: Friendship Is Magic comic issue #9-10, "Zen and the Art of Gazebo Repair", Big Macintosh is too focused on his quest to obtain nails for said gazebo to notice that two girls (Fleetfoot and Tealove) have fallen head over hooves for him.
In Fly A Little Faster Stiles is extremely oblivious to just who Derek is actually in love with. Until the evidence gets too much for him to ignore. Unfortunately at that moment Ennis attacks.
Turned Up to Eleven in Kyon Big Damn Hero, with Kyon completely unaware of the affections of Haruhi, Mikuru, Nagato (sort of), Kanae, Tsuruya, and many of the girls in his school. Until his shoe locker is filled with notes from those girls, that is. He's also incapable of spotting the polyamorous relationship that several other characters share. Even Mikuru worked that one out.
In the first episode of The One I Love Is Rei gives Shinji a chocolate heart, much to his surprise. Hikari then tells him Asuka is in love with him, much to his utter amazement and disbelief.
Peggy SueFix FicThe Second Try subverts the trope. Everyone think Shinji and Asuka are oblivious to each other's feelings... but in reality they not only are well-aware but also they got married before returning to the past. But since they don't want anybody finds out they are time-travellers, they pretend they are blind to each other's feelings.
Frodo in The Very Secret Diaries is oblivious to the fact that every single member of the Fellowship wants in his pants, and tries to flee to Mordor when he figures it out.
Sam coming too. Good thing, as will enable me to have more of those platonic, brotherly foot massages he's so good at.
Take any franchise where there are multiple love interests bet that there will be at least one character who is oblivious to the affections of another notable character. This is also applicable to original author made characters as well but this is harder to develop so it is rarely done well.
In Hunting The Unicorn, Blaine's trust in people and his inability to gauge when people are interested combines this into Fridge Horror: If Blaine didn't get the picture when Kurt was all but throwing himself at him, nor when his old high school friend tried to invoke a Dance of Romance, it's only logical that he has no clue when someone is stalking him.
Twilight: Dash, has anypony ever had a crush on you? Dash: I don't know. Maybe? Twilight: Well, one does now... Dash: Who is it? Twilight: [Face Palm]
Twilight is more often on the receiving end of this trope; for instance, in the fic "Twilight Learns a Secret", she got several months into her relationship with Dash before she even realised she was in one. And that was only because RD kissed her, and then spent several pages explaining the situation. Possibly with diagrams.
In Divine Jealousy And The Voice Of Reason, Twilight Sparkle in quick succession learns that Fluttershy and Bulk Biceps are lovers, that Rainbow Dash and Fluttershy are no longer lovers, and that Pinkie Pie has a crush on Cheese Sandwich. Twilight also sees all the clues but fails to realize that Rarity and Spike are falling in love, too. Twilight also imagines that nopony realizes that she is falling for Princess Luna, though she's in point of fact not fooling anyone.
In The Shoebox project Sirius believes that Remus is oblivious to love.
Kissing Lily was being touched with purpose but even that was sort of a joke, and now he's thinking about kissing, and is that why Sirius has licked his lips twelve times in the past thirty seconds? "Oh," Remus says suddenly. "I get it. I'm rocks."
In Game Theory, Tiida Lanster completely fails to notice Rizu's massive crush on him.
Rika Nonaka in the Tamers Forever Series. In this case it's justified since Rika is unable to believe that anyone could possibly even like her, much less love her.
In the Sherlock fanfic Baker School Blitz, Jim, despite picking up nonexistent hints that John may be in love with Sherlock, is frustratingly oblivious to the fact that his best friend Sebastian has been nursing a painful crush on him for years.
In thisTomb Raider (2013) fanfiction, Lara is this trope (as opposed to her mostly asexual portrayal in canon.) Lara admits in her own narration that she 'needs' Sam, the two sleep in the same bed every night, she feels jealous when a boy pays attention to Sam, and yet it takes several weeks before she realizes that her feelings for Sam might be romantic. Sam's response to Lara's eventual Love Confession:
Sam: I told myself I wouldn’t say ‘finally.' But—god—finally!
Naruto in Escape from the Hokage's Hat. In part due to No Social Skills and in part the people around him not giving him any relationship to learn from or anybody teaching him about it. Kakashi is a single man who reads smut in public. Anything Jiraiya says is written off as bullshit by Naruto. Sakura's failed attempts to get Sasuke's attention won't help Naruto any. Tsunade would only bring up her dead boyfriend. Shizune is single and tends to tease him relentlessly on the subject of relationships. Sasuke is a Celibate Hero who finds love annoying. Compound the fact that he's going through puberty and you get one very confused little boy. A confused little boy who thinks that finding someone attractive means you're a pervert.
A defining plot point in Magician's Obsessions. Anypony who cares to look will notice that Twilight and Trixie are head over hooves in love with each other, but Trixie's egotistical stage persona keeps her from seeing Twilight as anything but a Worthy Opponent, while Twilight's lack of social skills makes her think that what she's feeling is only very intense friendship. Even though Twilight was suffering a severe depression due to longing for Trixie, while Trixie has an entire shrine with pictures and news clippings about Twilight.
Celestia: At this rate I may need to send her a book on the subject, or perhaps just write her a message telling her she is in love. For being my smartest student to date, Twilight is also sadly the most dense.
Shining Armor in Stallionsof Harmony Verse doesn't register dozens if not more mares (and stallions) that like him, even if you tell him that directly in the face. He treats their confessions and love letters as 'pranks'.
Spitfire doesn't realize that her best friend, Soarin, is in love with her for years. To be fair, he never told her outright, only gave hints which she missed.
A new world: Story of a lost Shinobi: Subverted. Naruto and Mirajane openly flirt and tend to indulge each others Covert Pervert. Due to this, Natsu goes to Naruto for advice on how to start dating Lucy and Gray is less dismissive of Juvia's feelings what with having Naruto's interactions with Mira giving them perspective.
In a real heartbreaking scene from the A Certain Magical Index fic, Twist Of Fate, Touma tells Index that he's seen how happy his parents are with each other and would like to have a similar relationship with a girl, but he fears that no girl would ever want to be with a misfortune "loser" like him. Index walks away and cries, realizing that he hasn't picked up on her feelings or that of pretty much every female character in the fic. He remains so dense that he doesn't pick up on Misaki and Seria's feelings even after they all go out, get drunk, and spend the night together.
In Naruto: the Secret Songs of the Ninja Naruto loans Hinata his forehead protector (she left hers behind when she ran away from home) as a sign of how much faith he has in her during a fight, something which gives her enough strength to win. When they get back to Konoha and she retrieves her own, she asks Naruto if she can keep his and let him have hers to replace it instead. After pondering why she'd want the forehead protector he received from Iruka-sensei rather than the one she earned herself, he has a Eureka Moment- because him having Iruka's old forehead protector is like having part of Iruka with him at all times, obviously Hinata is comforted by having part of Iruka with her as well. He even observes that him wearing Hinata's forehead protector means that it's like she's always with him now, but doesn't think anything of it other than "that's pretty neat".
Lampshaded in the lemon fic Physical Exertion: eventually Pyrrha gives up and just asks Jaune- an eighteen-year-old boy- if he even knows what sex is. His answer is rather ambiguous, although given that she then jumps him, that's neither here nor there.
History's Strongest Shinobi: Naruto and Kenichi. Kenichi only has eyes for Miu. Naruto has gone on record to state "I'm shit with girls." and of the girls who like him one sees him as Just a Kid, there is too much baggage associated to another and the third is a downplayed Tsundere who's not trying to rush revealing her feelings.
Ted, the gym manager in Burn After Reading, is in love with Linda, who looks everywhere for a man and wants several rounds of cosmetic surgery to improve her odds. In the end, he does something heroically stupid to try and help her.
Joe Dirt is pretty good at picking up trashy redneck women, but when it comes to sweet girls, he thinks they're just being nice.
Sky High: Will Stronghold is oblivious to Layla's crush on him, although he does have the excuse that Gwen Grayson got him to fall in love with her, then pretended not to notice herself in order to better string him along (Even though when it came time the reveal that 'it was mutual', he couldn't take the hint until she flat-out said it).
Mark from The Room, to a ridiculous extent. He never gets the idea that he's helping Lisa, who is Mark's best friend's Johnny's fiancé, cheat on Johnny until about the fourth or fifth time that Lisa calls him over to have sex.
In X-Men: First Class, Charles doesn't notice that Raven harbours some non-sisterly feelings towards him.
Edgar Rice Burroughs generally had oblivious heroes. Special mention must be made of Tan Hadron, the hero of A Fighting Man of Mars, who actually managed to not realize he was in love with Tavia instead of Sonoma after 1) he had seen beautiful women and the first comparison that had popped to mind was to Tavia, 2) he had been betrayed, and when he realized it was Sonoma and not Tavia, his first words were that he was glad it was not Tavia, 3) After which he begs Tavia never to leave him as he cannot live without her, and 4) he had taunted Sonoma for her cowardice by saying he had fallen in love with someone else, a slave girl, and someone else had pointed out he had obviously been talking about Tavia. Indeed, he denies it then — although admitting a few days later.
In Sandy Mitchell's Warhammer 40,000 novel Scourge the Heretic, Mordecai is oblivious to the attraction that Keira, another character in the Inquisitor's retinue, feels for him. Partly because it is expressed in a rather truculent manner (until another woman points out to him that it could be attraction), partly because Keira, who was raised in a Sex Is Evil cult, does not realize it herself until she accuses Danuld of wanting to sin with her, and he tells her that he can tell that he doesn't have a chance because of Mordecai.
In Dorothy L. Sayers' Gaudy Night, when Lord Peter Wimsey is being criticized for how he spends his life, Harriet Vane snaps back: perhaps he catches murderers for fun, but he does it, and he could be killed, and many innocent people have reason to thank him for it. She reflects afterward about what her reaction shows about her own attraction.
Bluefur in Bluestar's Prophecy also evokes Firestar Syndrome throughout the book. It takes three different cats to get her to admit that Thrushpelt has feelings for her, despite the fact that he was frequently staring at her, inviting her on patrols, and cracking jokes that only seem to irk her.
Not to mention the fact that she didn't even realize her own not-so-subtle attraction to Oakheart until he confessed his love to her.
One story in Mack Reynolds' Section GSpy FictionIN SPACE! had Li Chang Chu abandon subtlety, pointing out to top agent Ronny Bronston that they were alone together in a stateroom with the door locked and no other demands on their time. Particularly funny in that he'd been hot for her about as long as she'd been for him, but didn't think he had a chance — despite being well aware that women found him very attractive. He just didn't realize this woman did, too.
Robert A. Heinlein's Juvenile books often had young male protagonists that were oblivious to girls. They were otherwise intelligent, so either they were just blind to people or just not interested in females. However, one of his stories (The Menace From Earth) it's not the male who is oblivious but the girl. She is very upset when her best friend and future business partner develops a crush on a tourist she is guiding (the 'menace' of the title) but only because it will 'break up the firm' - yeah, sure. Also a case of Everyone Can See It; the girl's best friend, the 'menace' herself, etc.
This was a case of Executive Meddling — Alice Dalgleish, children's book editor for Charles Scribners & Sons, had very firm opinions on how much "suggestive" content was "proper" for juvenile novels ('zero' being the highest permissible level), and ruthlessly quashed anything Heinlein wrote that even remotely hinted that teenaged males might possibly have a sex drive. Heinlein didn't even try to write romance into his stories until after he changed publishers and stopped writing juveniles. (The Menace From Earth was not first published by Scribners, note.) Also, even though Dalgliesh was an extreme case, virtually no editors in the 40s and 50s would approve anything but the most ultimately chaste romance material for young adult novels.
It may have been Executive Meddling, but the girls in the stories were practically ripping their clothes off and the guy was just utterly clueless. "Gee, why did she take my side against her own uncle and risk everything for me and spends time with me and is always ready to help me with anything I need?" "I guess she just wants to be my very good friend". HELLO?!
In Harry Potter, Ron is totally oblivious to Hermione's feelings for him until the sixth book or so. This is especially apparent in the fourth book, when Ron is desperately trying to find a girl to go to the ball with and suddenly remembers that Hermione "is a girl too". Hermione is upset that Ron didn't think about her immediately and she goes with Victor Krum from the Bulgarian school instead. Ron is angered by this but doesn't realize the ''real'' reason for his anger, even though Harry does.
Also, in their childhood, Lily to Snape.
And of course, Ginny Weasley fancies Harry since the very first book (it's more obvious in the second one, though) but Potter doesn't even acknowledge her before way later.
Well, in book 2 he seems to realize she likes him, but by book 5 she's dating other people and he's bummed to be suffering from an Unrequited Love Switcheroo. It turns out she's still into him, though, and they eventually get together.
In the Ravenloft novel Vampire of the Mists, young priest Sasha is oblivious to the huge crush the thief Liesl has on him. Partly because he was so in love with Katya (who's really The Mole), but after he realized that Katya is really a werewolf....
In Child of the Hive Drew is oblivious to Rachel's crush on him for most of the first part of the book. This is mainly due to Rachel's nerves, meaning she struggles to approach him.
The whole point of Swedish youth novel "Det är sĺ logiskt, alla fattar utom du." (Rough translation: "It's so logical, everyone gets it except you.") Nerdy boy and cute girl are best friends since always. The boy is in love with the girl, also since always, but the girl only dates sullen musicians and has no idea her best friend is in love with her.
Despite the numerous things he does for her, Gone with the Wind's Scarlett is completely oblivious to Rhett's love and devotion, and she is similarly unaware and unappreciative of Melanie's friendly affection for her.
One of the main points of Jane Austen's Pride and Prejudice is that Elizabeth thinks Mr. Darcy dislikes her (and she is angry at him, mostly due to misunderstanding) until he bluntly confesses that he is in love with her.
Similarly, in Sense and Sensibility, Marianne Dashwood has no idea that Colonel Brandon has been quietly and deeply in love with her since almost the instant they met.
In Josepha Sherman's The Shining Falcon, Ljuba intends to use Finist for her ambitions. She insists on this to herself whenever unpleasant thoughts, such as it hurts not to be trusted by him, occur.
In L. Jagi Lamplighter's Prospero's Daughter trilogy, Miranda. Although the one in love with her did explicitly tell her that love between her, a human, and him, an elf, is as impossible as love between a falcon and a dove.
Anne of L. M. Montgomery's Anne of Green Gables series initially spends quite a bit of time hating Gilbert Blythe for his extraordinarily bad first impression, but even after they finally become friends, she remains completely oblivious to the feelings he's been holding for her from day one. When he asks her to marry him, it blindsides her completely. Never mind the fact that the entire town of Avonlea knew of Gilbert's feelings and were waiting with bated breath for them to get married.
Anne actually takes it one step further. Not only is she oblivious to Gilbert's feelings for her, she's also oblivious to her feelings for him. Not denial. She simply has no idea that she's fallen in love with him, thanks to the highly unrealistic ideas she has about what being in love is supposed to be like.
Alec Lightwood from The Mortal Instruments is a rather... odd example. Despite the fact that he and Magnus were dating, he is caught completely by surprise by Magnus's Anguished Declaration of Love in City of Glass. In his defense, he was still hung up on Jace, and his relationship with Magnus was just supposed to be a casual thing. He gets over both Jace and his obliviousness by the end of the third book, though.
Mutual obliviousness in Mort. Mort himself spends most of the book under the impression he's in love with Princess Keli, what with the Rescue Romance and everything. He's wrong. Ysabell spends most of it under the impression she wouldn't marry Mort if he was the last man on the Disc. She's wrong as well.
Another Discworld example is Mr. Bent in Making Money who doesn't realize that the head clerk Miss Drapes is in love with him. At least not until she comes to get him after a nervous breakdown and he's let his clown side take over. At the end, they do get married in the Fools' Guild.
In Elizabeth Peters' Amelia Peabody mysteries, Amelia spends a whole book completely oblivious to the fact that the 'master criminal' she is tracking down is in love with her. Her husband Emerson, however, is not so clueless and gets increasingly annoyed at both the criminal and his oblivious wife. Hilarity Ensues.
It runs in the family, too. Their son, Ramses, spends a not inconsiderable amount of time pining after their adopted daughter, Nefret, who thinks they are Like Brother and Sister.
As a perpetual child, Peter Pan is literally unable to understand the concept of romantic love, and regards all female characters either with indifference or as potential mother figures. This wouldn't be much of a problem...except that every female character, be it fairy, mermaid, girl or mother, is attracted to him in some way.
In P. G. Wodehouse's Hot Water, Packy sees Jane after his engagement is broken and realizes he's been in love with her all along.
In the tenth book of The Dresden Files, Harry fails to realize that Luccio is flirting with him when she bathes herself topless in front of him (he'd been asleep for hours, but she waited until he woke up), which leads to this immortal line:
Molly is head-over-heels in love with Harry, and he's the only one who doesn't know, despite cutting her crush in him off at the knees when he took her on as his apprentice. In Ghost Story, he realizes the absolute depths of her affection for him, but he's dead.
Part of this may be explained by the fact that his own mentor used the sexual development of both of his apprentices for his own nefarious purposes. That, combined with Harry's own issues with protecting women (especially a woman he sees more like a daughter or niece), means it would be nearly impossible for him to "take advantage of" Molly, despite the tradition to do so among wizards.
Deconstructed in Zadie Smith's White Teeth. Irie (and half the women in North London, it seems) desperately want to believe Millat is this. He isn't- he's just a jerk.
Marius from Les Misérables is oblivious to Eponine's feelings for him, being blinded by his love for Cosette.
Katniss Everdeen from The Hunger Games really takes this to a whole new level. Peeta Mellark confesses that he's in love with her on live television, risks his life to save hers on numerous occasions, tells her about when he first fell in love with her, craves her affection and attention, refuses to let her risk her life for him and later implores her to kill him so that she can win the Games. When she refuses he removes the tourniquet on his leg so he can bleed to death and thereby make her the winner. After they have taken a third option by threatening double suicide and both gotten out of the games alive Haymitch tells Katniss that she needs to make people believe she's in love with Peeta or else they will be punished for making the Capitol look foolish. Katniss responds by asking if Peeta has been informed and when Haymitch points out that "he's already there," Katniss thinks he means that Peeta knows they need to fool everyone. It's not until she breaks his heart on the train ride back home that she begins to realize that perhaps he's in love with her for real.
Not to mention, the fact that her best friend, Gale Hawthorne, tells her in the second book he has loved her for a lot of time, and she was always oblivious to it.
Her obliviousness might be because of her unwillingness to actually find love, after seeing her mother become a shell when Katniss' father died.
Spencer from Pretty Little Liars takes a little while to realize that her academic rival Andrew Campbell has developed feelings for her.
Kaala is this in Dorothy Hearst's The Wolf Chronicles. The reader initially thinks that it's because she's a wolf (and the trilogy depicts wolves very realistically) but then we see other romantic relationships form and it becomes clear she's just clueless.
To clarify: Azzuen starts following her around after she saves him from starvation, and this continues even after they grow up. He becomes extremely loyal to her, even breaking pack laws to support her. He violently drives off another male wolf who expresses interest in Kaala, and later follows her into exile away from, oh, the only family he's ever known. When Kaala starts Taking A Level In Jerkass, he snaps her out of it with a speech that basically goes 'I'd like you to be my alpha, but not if you're going to be a bitch about it.' All of the above is narrated through Kaala's perspective, and yet she must literally read his thoughts to realize that he's been in love with her since puphood.
It is justified, though, in that a female wolf, Marra, is similarly loyal to Kaala and does many of the same things. (An elder comments that Kaala is strong, a potential alpha, and it's natural for wolves to follow the strongest among them.)
Corie in Summers at Castle Auburn, painfully so. She doesn't see when someone is in love with her, and she's very bad at figuring out who is in love with who.
Since Idlewild is told from Halloween's perspective it's impossible to guess that Pandora is in love with him until her reveal.
Played straight again at the Christmas party where Sherlock deduces that Molly must be off to see a new boyfriend because she's dressed up and has very carefully wrapped one of her presents - completely failing to realise it's intended for him. Which even he apologizes for afterwards.
Mr. Boynton is either shy or downright oblivious throughout the radio/television series Our Miss Brooks.
Unless you count the time he took her to the dance, and suggested they might go off together. In a subversion of the Anguished Declaration of Love, she is completely disgusted by the idea.
On the other hand, when she asked him to ride with her, he dumped Delia, then lied about it to Angela. When Angela saw Delia at the dance, the jig was up. In other words, he was just as oblivious to Delia's crush as she was to his. Maybe even more so.
Seems to be the set up for Barney and Robin in How I Met Your Mother — Barney actually tells Robin that he loves her in "Benefits", but she thinks that he's commenting on Ted's neediness.
In season seven, it's Barney's turn to be the oblivious one.
Clark regarding Chloe's feelings for him in Smallville. But under the influence of Red Kryptonite or other forms of Phlebotinum, Kal repeatedly taunts her with the truth that Clark just doesn't feel that way for her.
Not always though, Chloe got a nice long make out session with him in Rush, the second time he is affected by red kryptonite.
There are two examples of this in Season One. Xander develops a huge crush on Buffy, who is oblivious to his advances until he asks her to the dance in the season finale, while he himself is unaware of Willow's feelings.
There are hints that Buffy is aware, just uninterested. Xander, on the other hand, is oblivious to Willow's feelings feelings for him.
In Season Eight, when Buffy's loneliness and need for stability compels her to go to Xander. Xander declines, having long since decided he and Buffy are Better as Friends.
In the Season 5 Angel episode "Smile Time," Wesley is the one who informs Angel that Nina obviously has feelings for him, all while ignoring the hints that Fred loves him. It takes a direct kiss from Fred for Wesley to notice, but he reciprocates quickly.
In Pushing Daisies, it was a while before Ned twigged that Olive had romantic feelings for him, despite some really blatant flirting on her part in the first episode.
A psychiatrist on Bones tells Dr. Sweets that only one of the Booth/Brennan pairing is aware of their mutual feelings. Since Booth is normally the best with emotions and has shown more signs of being possessive and jealous, we're left to assume that Brennan is the oblivious one. Entirely in keeping with her nature, though.
It is implied that this may partially be the cause of Mal and Inara's UST in Firefly, at least on Mal's side. The episode "Heart of Gold" very strongly indicates that while Mal is attracted to Inara, he is unaware she is attracted to him.
It's very possible Mal is a rare male version of the Broken Bird variant of this trope, and despite his insults and Hypocritical Heartwarming doesn't think he's worthy of her. It's why her calling him a petty thief hurts his feelings so much.
Simon is oblivious to Kaylee's feelings for him because of his preoccupation with his sister's recovery. In "Serenity" he makes his Anguished Declaration of Love right before a fight with the reavers, and he apologizes to Kaylee for not recognizing her advances, and confesses that his biggest regret is never being with her - which causes the quivering Kaylee to Take a Level in Badass so as to live to take him up on it.
Maxwell is completely oblivious to CC's crush on The Nanny.
Made even more hilarious by all the snide comments Niles makes, because literally Everyone Can See It, just not Max. (I do mean everyone. Even Gracie, although considering how precocious she was as a kid, that's not very surprising.)
This came to a head in a season two episode where Chakotay and Janeway both contracted a terribly infectious virus, and were left on a planet with an atmosphere that could keep the virus at bay while Voyager went on. Their UST was off the charts, but it culminated in Chakotay telling a 'story' that described how he cared for her and would be happy just staying by her side, whether her feelings were reciprocated or not. They never even got to kiss.
Of course, Kira's obliviousness is quite justified as Odo deliberately refuses to let his feelings show.
Amusingly, in a DVD extra Nana Visitor remembered that at the time she thought it was ridiculous that Kira could work that close to someone and not realize he had feelings for her - until her co-star Alexander Siddig revealed his feelings for her (the two went on to marry).
Stargate Universe: Chloe at least acts like this for most of the first season, until the finale episode, where it's made clear she isn't quite oblivious as she appears.
The Doctor to Martha in Doctor Who. Eventually, she gives him an Anguished Declaration of Love, which they subsequently agree to ignore in order to preserve their friendship. Later on, he describes to her a device that keeps them hidden from the hypnotised public to her as "It's like when you fancy someone, but they don't even know you exist." He rushes off, and Captain Jack reads her expression: "You too, huh?"
Amy: "I nearly died! I was alone, in the dark, and I nearly died. And it made me think."
Doctor: "Ah, yes... Natural. I think sometimes. Well... lots of times."
Amy: "About what I want. About who I want. You know what I mean?"
Doctor: "Yeah. ...... No."
Amy: "About who... I want."
Doctor: "Oh right, yeah. ...... No. Still not getting it." note He wises up after she kisses him.
It goes the other way in "The Lodger", when the Doctor is able to immediately recognise the UST between two other characters who are both afraid to admit it out loud. This and other cues in the series suggest that he is aware of his companions' feelings, but ignores them to avoid relationship issues (or possibly just because he has issues). Or perhaps he is only oblivious when it directly involves him. (In one of the Doctor Who New Adventures books he responds to a blatant come-on by saying "I'm well-known for failing to notice such things, or getting them slightly but distinctly wrong. It saves so much trouble.")
He also deliberately suppresses romantic attraction, since any human he gets involved with will age and eventually die, in what would appear to him to be no time at all. Avoiding being reminded of this might even be why most of his companions are young. (Which the Dream Lord enjoyed pointing out to him.)
Amy was oblivious to Rory for years, assuming he was gay when he never showed interest in any (other) girls. And Rory was oblivious to the fact that Amy really loved him; originally, he assumed she was in love with the Doctor.
By contrast, Ten and Donna were decidedly not interested in each other, but it became a Running Gag that they were mistaken for a couple.
At the end of "Triangle" Mulder flat-out says "I love you" to Scully. Her only response is to mutter an exasperated "Oh brother" and walk off. Admittedly Mulder had just been raving about how he and Scully had just saved the world from the Nazis back in 1939, so Scully clearly felt Mulder had hit his head too hard, not realising it was actually a matter of her hitting Mulder too hard. And it's not like he was really keeping it a secret before that. Several characters had mentioned it or assumed they were together.
Mulder and Scully routinely ignore obvious signs that the other has feelings for them. In the first movie, they have an Almost Kiss but both ignore it. Then a writer who is known to get in people's heads literally says to them, "Agent Scully is already in love." Of course, they both ignore it.
Even the actors found it ridiculous.
David Duchovny:(on what he would say to Mulder) For Christ’s sake, fuck that girl. Look at the way she’s looking at you. Are you blind? Why do you think her mouth is always open?
Conversely, Doggett tends to be oblivious to Agent Reye's feelings for him.
The entire sixth season episode "The Rain King" more or less revolves around this trope.
In Robin Hood, Robin was more or less oblivious to Kate up until the time they got together - and then for most of the time after that as well.
Andy is oblivious to April's crush on him. As of Season 3, April and Andy are in a relationship, but now it's Leslie who doesn't seem to notice Ben's growing crush on her.
In Season 3's "Soulmates", Leslie is the one who asks him out first, though to her dismay Ben turns her down due to Chris's anti-fraternization rules. He does initiate their first kiss, though.
On Zoey 101, Zoey is oblivious to Chase's feelings for her. This gets painful when it drags on for three years, despite multiple attempts by Chase to tell her his feelings. She's oblivious even after she is told flat-out by her friends that Chase is in love with her, and had been since he met her. Lola even goes so far as to pull a random student from the hallway. And Zoey still doesn't believe it!
Lola: Ginny, could you come here a minute?
Ginny: What's up?
Lola: 'Blank' is in love with Zoey. Fill in the blank.
Lola: Thanks for playing.
On iCarly, one of Zoey 101's Spiritual Successors, it's inverted, with Carly completely aware of Freddie's love for her. It's mentioned in their first scene together with Carly asking Freddie to get over the crush he has, but it fails to fade away, and as they grow up, his crush blooms into a serious case of Just Friends love for Carly.
On Glee, Blaine had no clue that Kurt saw him as anything more than a friend. And Kurt's not exactly subtle when it comes to his crushes. It got to the point where (after helping Blaine serenade another guy on Valentine's Day), Kurt flat out told Blaine that he thought he was the one about to be swept off his feet. Blaine seemed plenty sympathetic... until the next episode, when he expected Kurt to be perfectly fine with him dating Rachel, and the one after that, where he tried to give Kurt sex advice and told him that his seductive faces looked like he had gas. Face Palm.
In season 3 Blaine is at it again, this time unaware that he has a Stalker with a Crush in the form of Sebastian.
On Castle, Beckett is guilty of this in the first season finale. Castle himself is guilty of this in the second season finale and again in the third season opener, when he can't understand why Beckett is so upset with him for not calling immediately when he got back into town. By season three's finale, neither one is oblivious anymore. It goes something like this:
Castle: (concerned) I'm your partner, Kate. I'm your friend.
Beckett: (angrily) Is that all we are?
Castle: (angrily) Yes. No. I don't know. We kiss and then we never talk about it, so no, I don't know what the Hell we are.
In the last scenes of the third season finale after Kate is shot, Castle outright declares to her that he loves her. Whether she'll remember is another story.
Leave it to a show like Castle to make the drama even cheesier. She remembers all right. She's just faking amnesia.
Throughout season four they seem to go back and forth with the Oblivious Ball (most noticeable when Castle finds out that Beckett lied about not remembering what happened when she was shot and subsequently went back to his bimbo a day habit) until the finale. They sure as Hell aren't oblivious anymore.
Sergeant Bruce Hornsby is completely oblivious to Corporal Angie Ogden's interest in Red Cap.
In Scrubs Ted is so oblivious to Gooch's subtle (and not so subtle) hints she's attracted to him that she assumes he isn't interested and is just too nice to say. Though Ted musters up the courage to tell her it's because he thinks she so great he couldn't have imagined her actually feeling the same.
Gooch: I'm an idiot. I've been dropping all these subtle hints that I like you. Sideways glances. The secret smiles. Telling you I wanna screw you. You're clearly not interested.
Josh on The West Wing. Donna is in love with him for years and he doesn't notice. Then when they kiss he apologizes and seems to worry that he's wronged her. She responds by trying to hand him her room key but the whole thing is inadvertently thwarted by a member of the Santos campaign and he seems to just forget about it. When they finally do sleep together (on her initiative) he still worries that she needs space and that she regrets it.
He also seems completely oblivious to the fact that Amy is still in love with him at the start of season four.
Isobel Crawley of Downton Abbey manages to give the "I Don't Want to Ruin Our Friendship" speech to Dr Clarkson without realising she's giving it. And literally has no idea that he's not only in love with her but openly courting her. Wow, Isobel. Wow. She is generally a clever woman, but that takes a special kind of obliviousness. Whether she wises up or not remains to be seen, but if she's not desperately in love with him (and oblivious to that, as well), somebody needs to tell Penelope Wilton, because she's sure as hell playing it like she is.
In the majority of the first two seasons of House of Anubis Mara is painfully oblivious to Jerome's crush. (She is also somehow oblivious to the entire mystery but that's a different story.) It gets to where she fake dates him to make her long distance ex jealous, and this exchange occurs-
Mara: Look at these pictures, it looks like you're really in love.
Jerome: *Staring at her longingly and not listening* What?
Mara: I said, you're a really great actor.
Get Smart: Depending on the episode, Max was either oblivious to 99's feelings for him, or aware (and felt the same) but was too socially awkward to show it. This actually continued right up until the point that he proposed to her.
Salem: John Alden is unaware of Anne Hale's feelings for him, and he doesn't trust that Mary Sibley still cares for him no matter how many times she risks herself to protect him from the witches.
In The Worst Year of My Life, Again, Alex has absolutely no idea that Maddy has a crush on him. It's suggested that it's because they've known each other since they were very young, so he just doesn't think of her like that.
Doesn't he know that I've had him memorized for so long?
Anne in A Little Night Music is not only oblivious to her awkward stepson's feelings for her, but also to her own feelings about him, which she only realizes at the end.
In Les Misérables, depending on the actor, Marius can sometimes come off as quite a bit thick in the head about this with Eponine.
In The Sound of Music, Maria has absolutely no clue the Captain is in love with her until the Baroness (for her own ends, of course) points it out. This is possibly because Maria has spent too much time in a convent. A moral crisis immediately ensues, which the Reverend Mother very nicely clears up.
Cyrano uses Selective Obliviousness to refuse to comprehend that he can be loved even with his enormous nose. At Act I Scene V, Le Bret has to remind him of the Smitten Teenage Girl Cyrano meet some moments ago. At Act IV Scene IX, Christian stubbornly tries to convince him that Roxane loves his “soul” – Cyrano – instead of his face. Cyrano will not believe it. Justified because Cyrano has serious Mommy Issues and his upbringing makes him more confortable being the Love Martyr.
In Seussical, Horton is unaware of Gertrude's crush on him, even when she sings a song about it straight at him (he's too busy talking to Whos). This arguably changes after she reveals her Determinator tendencies in "All For You".
In MARDEK RPG, Chapter 3, Elwyen is obviously head-over-heels for Mardek, but Mardek doesn't notice because he's a moron.
In Metal Gear Solid 3, Naked Snake is very oblivious to Ocelot's infatuation with him. EVA teases Snake about how dense he is about it. Even Gene from Metal Gear Solid: Portable Ops remarks on how Snake "caught Ocelot's eye," prompting Snake to ask confusedly what Ocelot has to do with anything. Of course, Snake (and his later clones) isn't known for being the brightest when it comes to romance...
Depending on your choices in Neverwinter Nights, Aribeth may lament at the end that she never noticed how the player character felt about her until it was too late.
Fire Emblem loves this trope with its lords. Both Roy from Fuuin no Tsurugi and Ephraim from The Sacred Stones are fairly oblivious to the affection of their various possible love interests. Ike from Path of Radiance and Radiant Dawn, however, takes this obliviousness to entirely new levels and never quite gets it despite all the women who have expressed interest in him. There are, of course, otherexplanations.
Played as a game mechanic in Pokémon; some Mons have the trait Oblivious, which prevents the "infatuated" status condition. It's mostly held by dim-witted Pokémon, like Slowpoke and Whiscash.
Link in The Legend of Zelda: Ocarina of Time is completely unaware of the fact that Princess Ruto believes them to be engaged. Of course, he's completely unaware of the interest of just about every other female character in the game too.
We don't really know that because Link is a silent protagonist.
He does seem a bit creeped out by Saria though, since he is seem slowly backing away from her before taking off full-sprint when leaving Kokiri Forest for the first time.
He's not much more observant in Twilight Princess, either, where both childhood pal Ilia and pint-sized Deadpan SnarkerMidna have a thing for him. The closest he gets to catching on with anyone is when he shares a brief hand-holding scene with Princess Zelda...and she doesn't seem to have any real romantic feelings for him in this game. And after the final battle, Link drops the Master Sword, and sprints to Midna's side to make sure she's alright. Then when she leaves for the Twilight Realm, he all but weeps.And one could argue that Link not only knows about Ilia (and/or Midna's) feelings, but even reciprocates them. And after all, the guy lets a royally important trip get interrupted (and gives the plot time to start) because Illia is mad at him for scratching the horse's leg. Sounds pretty whipped, doesn't it?
Not to mention, in Wind Waker, judging by the embarrassed look on his face, Link immediately picked up what the Fairy Queen meant when she said that he was "just her type."
In the Backyard Sports series, Marky Dubois is in love with Billy Jean Blackwood. Billy Jean is oblivious to Marky because she believes he has cooties.
Terranigma has Meilin, who eventually decides that she's in love with Ark. She then proceeds to make overtures to him, only to get (albeit amusingly) shot down because Ark is too busy worrying about Elle.
Meilin: You know, Ark...I have stories to tell, too.
Ark: Look! This is Elle's house!
In the Tales Series it's fairly common to have The Hero be this trope (and if not them, than another party member).
In Tales of Symphonia, Sheena practically confesses her feelings to Lloyd in one possible scene, and he doesn't realize it.
Tales of the Abyss, Tear falls in love with Luke, and he's the only character in the party that doesn't pick up on it (which is saying something since one of the characters, Anise, actually appears to be dumber then Luke for the most part).
Of course, Tear is not very good at voicing her emotions due to being raised as a soldier her entire life. The fact that Luke is a Replica with only 7 years of life experience (most of that sheltered) doesn't help things.
A similar thing occurs in Tales of Legendia, with Chloe having a crush on Senel (which even the game's big idiot Norma notices). Senel at least picks up on Shirly's crush for him.
While Senel is pretty dense, he's also a Chaste Hero due to his rather troubled past, and it's implied that he'll probably never get to the point where he's capable of being romantically interested in someone.
In Tales of Phantasia, this is largely averted; none of the characters have too much difficulty recognizing each other's affections, but just about all of them refuse to assert themselves romantically before the last act of the game, probably because most of them are teenagers.
Karol actually does like Nan; thats why hey was so eager to get her attention at the begining of the game.
Pascal of Tales of Graces might be the biggest example in the whole series. When Hubert flat-out tells her that he likes her, she misinterprets it as him telling her that he's getting married. She cheerfully promises him that she'll be at the wedding, and will take a bath with soap as well. He slinks off, defeated.
Hubert's brother Asbel fits this trope due to not noticing Cheria's feelings. Although their case is a deconstruction as Cheria ends up bitter and angry at Asbel for not noticing even after the Time Skip (7 years... She spent them alone) whereas Asbel had a lot on his plate. To elaborate he couldn't protect his friends and brother from a monster, one of said friends pulled a Heroic Sacrifice for them to live (Hello Survivor Guilt) and his brother is sent off to another COUNTRY. Factor in that Asbel was 11. He ends up leaving home (for 7 years) to get stronger. Then after the time-skip he finds out that his dad is dead... Yeeeaaaah. Love was the last thing on his mind.
Asbel plays this trope straight in the "Future" arc that takes place 6 months after the main story. Having dealt with issues that plagued him in the main game, Asbel has finally gotten to the point where he's ready to think about such things; His mother has even started putting pressure on him to get married. And he's shown to be utterly clueless when it comes to romance. He apparently spent all his time at the Academy absorbed in his training, so it's safe to say he doesn't have a lot of dating experience.
Cheria: "So were there any girls at the (Knight) academy?"
Asbel: "Oh yeah sure. We even used to stay up and talk about what we'd do if we became knights."
Asbel: "Yeah. Me, a couple of the other guys and some of the girls."
Cheria: "Did you do anything else?"
Asbel: "Nah. We just talked."
Cheria: (visible relieved sigh) "Oh. Okay"
For bonus points when his mom gives him the marriage proposals, Asbel compares the girls to Cheria.
Oh dear oh dear Hamil in Tears To Tiara 2. Supreme tactician, strategist, and an incredibly charismatic leader who can't understand that the resident Goddess of War Tart is absolutely in love with him. After she 1) let him sleep on her lap 2) sing for him 3) hugs him tearily and emotionally 4) cheers him up and calms him down 5) states in no uncertain terms she'll follow him everywhere and do what he wants 6) become angry and jealous when he talks about other females. And he still doesn't get it.
If Shepard woos Tali in Mass Effect 2, she'll confess that she's been in love with him since the first game. Since she ultimately wasn't intended to be a love interest, she obviously didn't drop any hints of her feelings during the first game. Then again, Shepard is the point of view character.
Until the end of that conversation, anyway... there had to be a reason for her mentioning her "nerve stimulation package" - aside from Fanservice, anyway. Unless she thinks he's gay.
Garrus with Dr. Michel. In the first game, he pulls a Big Damn Heroes move and suffice to say, she likes it. In Mass Effect 2, her letter intended to be written for Shepard almost immediately segues into checking how Garrus is doing instead. Finally, in Mass Effect 3, she buys him turian chocolates because she "saw it and thought of him"... and he still doesn't get it!
Possibly Fem!Shep with Garrus. In the second game he'll make a comment about some women finding scars attractive while staring at her. Averted if you take the Relationship Upgrade, during which she'll be very aware (and considerate of) his feelings.
Considering that Male!Shep gets a completely different line from Garrus and that the second game reveals his exclusive attraction to Fem!Shep, this seems highly likely.
This is the in-universe reason why MaleShep couldn't romance Kaidan until the third game. Shepard was too focused on work to notice Kaidan's feelings.
Kaidan: You were always so focused on work back then. The mission was everything.
Shepard: It's true. I'll never know what I missed.
In Tales of Monkey Island, Guybrush is oblivious to Morgan's feelings for him, especially noticeable in Chapter Three when they talk about how to calm the female manatee. Of course, this is due in large part to his unbreakable devotion to Elaine. (Even though he was more of a flirt in Escape From Monkey Island)
Add in the fact that Cloud himself was unaware he had feelings for Tifa until the Lifestream event.
Until the Lifestream event, he's a partial amnesiac with major identity issues, brought on by recovering (badly) from poisoning just in time to watch the guy who was protecting him get cruelly gunned down within sight of their destination, after both of them had been experimented on in an induced coma for four years. Oh, and the Big Bad mind controls him repeatedly for kicks until then too. The Big Badhe had already beaten. To say that Cloud's mind was not ready to even recognize romantic feelings is an understatement.
In Castlevania: Dawn of Sorrow, Hammer makes hints about having feelings for Yoko, but she never picks up on them, mistakenly thinking that he's "glaring" at her when he looks her way.
Akihiko Sanada of Persona 3 "seems to be completely incapable of recognizing female emotion," as the PSP version of the game states. He honestly has no idea why all those girls follow him around, and is similarly oblivious to the advances of the female protagonist if she pursues a relationship with him. He's not that great at understanding his own feelings, either; at the culmination of his Romance Sidequest, the protagonist herself must flat-out tell him that the feelings he just described having mean he's in love with her. This despite the fact that, if he is in the party during the July Full Moon event, he comes close to actually having sex with her under the Shadow's influence.
Hilariously, it seems like Akihiko is just the Cool Loner type, until the inevitable Beach Episode, where you discover that he is completely and totally useless in romantic situations.
Although really that's a component, albeit a large one, of the fact that he has the social skills of a brick; a result of having a grand total of one friend, himself a Cool Loner, for the first fifteen years of his life and having no time for anyone less dedicated than him.
Mitsuru provides a female example, as while she is slightly more in tune to emotions than Akihiko she still seems rather oblivious to the sheer amount of people of both genders who have crushes on her. For an extra bonus, her and Akihiko definetly have some sort of romantic tension but are too oblivious to actually act on it.
Hiroki in Canvas 2. Seven love interests and multiple students gunning for him and he's unaware of all of them.
Aveline in Dragon Age II is completely oblivious to Hawke's advances during her romance quest chain, even though s/he flat out says it at one point. In fact, she only seems to pick up on it after hooking up with Donnic.
Merrill of the same game is incapable of picking up on the advances of Hawke's brother, Carver. However "Mark of the Assassin" later implies that she was Obfuscating Stupidity to spare his feelings, since she's infatuated with Hawke instead.
As the player, you can also chose to have Hawke be oblivious to Merrill's obvious infatuation with Hawke, you know, if you're a heartless bastard. Of course, it works both ways, since Hawke has to explicitly state they are interested in Merrill before she finally gets the hint.
It could also be interpreted as sparing Merrill's feelings in a similar way to how she tries to spare Carver's. Telling her that she's like a sister to you before she manages to confess may cause her disappointment, but at least she isn't humiliated.
In the Tokimeki Memorial series, the main protagonist suffering a terminal case of this trope is a tradition. Every single one of them (be they a boy or a girl) is affected by this, but the severity of it depends from game to game. One of the worst is the protagonist of Tokimeki Memorial 2: every single main heroine, and both of his male best friends lampshade his total obliviousness at one point or another in the saga, and even several minor characters do it as well.
Raz during the first half of Psychonauts is a bit like this. Then again, he is ten years old.
Heck, after Lili blatantly states that she wants to make out with him, he spends the rest of the cutscene trying to comprehend what she was saying.
Played for laughs in the Smuggler questline on Tatooine in Star Wars: The Old Republic with a female Jedi who is completely oblivious to any flirting done by the smuggler, leading to this possible gem in the storyline climax:
Smuggler: (to Risha): Oh, I've got a Jedi and a Sith fighting over me, but I only have eyes for you. Jedi: Nothing you say makes any sense. Sith woman: Poor girl, she's never been kissed.
Shirou in Fate/stay night remains comically (or tragically, depending on your point of view) oblivious to Sakura's advances and obvious interest in him for many years. While he does find her attractive, all he wonders is whether or not this makes him a failure as a sempai, combined with the fact that she is the sister of one of his friends.
In Kanon, Yuuichi has been doing this regarding Nayuki's feelings for seven years straight. Probably the only reason that she hasn't given up or decided that he wasn't worth the trouble was because he'd already gone through too much at the time of the revelation. Indeed, in the end he realizes that his own amnesia is also caused by Selective Obliviousness— he wanted to forget the town where he "lost" Ayu.
In Lux-Pain, Akira is oblivious to romance in general and just doesn't seem to catch on to who has a crush on who. Unless you tell him straight out that this person likes someone else, he's not going to catch it. The best example is the guy Inugaku who has a huge, obvious crush on his dad. [Yayoi has to tell him outright that he's gay in order for Akira to understand...and that sends him into a humorous state of shock that doesn't last long.
A more serious example is when Sayuri calls him out on this trope technically and calls him a Jerk Jock that enjoys the women flocking to him and breaking their hearts. Naturally, Akira snaps only because Atsukiwas standing right there when she said that.
And of course, there's Akira's other friend Ryo who is also oblivious of affection from both the girls that constantly visit his store just to see him (and not buy books, which pisses him off) and his best friendHibiki and like Akira above, it has to be spelled out to him in order for him to understand. Only difference is that the person who asks him if Hibiki and him are going out is a Yaoi Fangirl and Hibiki isn't going to say anything.
In One Kagayaku Kisetsu E Kouhei can't understand why Nanase is disappointed when he takes her to cheap Ramen restaurant to try this new ramen, even though she is wearing an expensive dress and its Christmas Eve, in Japan, a Holiday for Couples.
Masayuki looks this way in Miku's route in A Profile.
This really doesn't help Tsukihime's Shiki out when you combine it with the Tohno Gland and penchant for attracting only people with superpowers or are dangerously crazy. By Kagetsu Tohya he seems to be at least a little aware, going out of his way to keep people like Ciel in his wanted harem focused on him. But still clueless to a baffling extent when you consider the six people in love with him in that story that he doesn't recognize at all.
Some of those are justified, though. Akiha is his sister (he thinks), Hisui has a crippling fear of men and acts quite cold, and he doesn't think Arcueid, being a vampire, is even capable of love like a human is. And to his credit, he does clear these up faster than most characters.
Kyoko in Kara no Shoujo is completely unaware of Uozumi's affections for her. It seems at first like Reiji is similarly oblivious to Kyoko, but it turns out to be a subversion.
Miles Edgeworth seems to be entirely unaware of the frothing masses of fangirls he has, let alone when females develop obvious crushes on him. Although he is all too aware of Oldbag's affection to him. Needless to say, it squicked him out. Lampshaded in Trials and Tribulations, when Gumshoe suggests that maybe the suspect (who Edgey vaguely recognised) was an ex who he forgot. His reaction? Genuine surprise, along with the genius line: "D-Do I really inspire this sort of frothing desire from the female masses?"
Speaking of Gumshoe, it is very strongly hinted that he has a whopper of a crush on Maggey, though she seems to be almost unaware of his attraction to her.
Apollo Justice is arguably worse: Juniper Woods tells him that she thinks he is wonderful while knitting hearts, and he still doesn't get a clue. Of course, everyone else can see it. It really doesn't help that Juniper speaks glowingly of Apollo, in a series where nobody in the rest of the series speaks glowingly of anyone else.
Bobwhite. Ben is the last person to figure out that Cleo has a major crush on him.
In Candi, the only member of the cast not aware of Jon's feelings towards Candi (up to and including his now ex-girlfriend) is Candi. Complicating things is the fact that Candi gets weirdly skittish when being pursued romantically, so Jon fears that if he confesses his feelings, it will wreck their friendship just as surely as a romance gone sour.
Hank in Catena is absolutely clueless about the fact that Treiss has a crush on him. Bear also seems to be rather oblivious to Ivy's attraction to him.
Justin in El Goonish Shive has had a deep crush on Elliot for years, which at least one other character knows and several others may suspect, but Elliot himself has never picked up on it. Elliot himself pretended to be oblivious to Sarah's flirtations so she wouldn't feel 'rejected' when finding out he already had a girlfriend. Yeah ... It Makes Sense in Context ... or at least in his own mind. (His girlfriend dumped him, came out as a lesbian, and started dating his twin sister / Opposite-Sex Clone, Ellen. He and Sarah are now dating.)
Mr. Verres, knowing there's a lot of Human-Uryuom offspring, managed to miss why his Uryuomsecretary constantly wears a very female human form and likes to sit on his table. Though he is pretty smart (otherwise Lavender wouldn't be attracted, for one).
In an interesting variation, both Elliot and Susan are aware they're utterly enamored with each other, but aren't aware that it's mutual. It's just a matter of who does their Love Confession first. In the meantime, nearly everyone else is also aware of it and some actively ship them.
Andrew Smith of Gunnerkrigg Court is an interesting case. He puts up with Parley because she's "hotter than hell", but manages to mistake her constanttsundere-style signs of affection for mockery. Then two strangers told him straight. Then she reacted on giving her a flower (a teacherset him up) by unconsciously teleporting them right into her bed. And starts to spontaneously teleport close to him several times per week. And he still was in the deep stunned surprise when she confessed.
Vriska Serket from Homestuck had no honest idea that her moirail, Kanaya, was in love with her. In fact, she thought that Kanaya had a crush on Tavros, the object of Vriska's (hate-filled) affection. There's also another moment where Karkat opens a memo, invites John and Dave into it, and starts ripping into them about 'flirting' with Vriska and Terezi. Cue John being thoroughly confused.
John is amazingly dense when it comes to this. Even after Karkat's lecture about avoiding sloppy interspecies makeouts, he still manages to interpret Vriska's invitation to go on a date as an offer to hang out and watch some movies as friends.
Karkat himself appears to fall victim to this, as it shown several times that Nepeta has a serious crush on him, yet he never acknowledges it. This is bizarre considering his expertise and intuition regarding romance. One later panel finally brings this up when he admits to another character that he is aware of Nepeta's feelings, but he doesn't reciprocate and has been deliberately ignoring the situation because there's just too much else going on to deal with it.
ZigZagged with Jake.At first he seems to be oblivious to his friends all having crushes on him, but soon proves that he's a lot more perceptive than people originally thought. However, when Jane tells him she doesn't have a crush on him, he accepts it immediately even despite her strange behaviour. However, while in a dreambubble later on Dirk, playing the role of his subconscious, suggests that he might have misinterpreted her, though Jake uneasily dismisses the idea. And through all this, he still appears oblivious to Roxy's genuine interest in him, unintentionally or otherwise.
The entirely one-way drama plays out in A Moment Of Peace. Crux, god of In-Between Places, is completely oblivious to the fact that the goddess of Stories has been crushing on him ever since they started talking at the base of Dawn Mountain.
Out There: Sherry is so very much oblivious to Ari's attraction to her, she thinks that since Ari looks at her differently than she looks at Miriam, it means Ari's attracted to… Miriam.  Meanwhile, Miriam, who has decided she's attracted to Ari, can't get Ari to realize it; Ari thinks she has embarrassed Miriam by offering her menial work. 
In Schlock Mercenary, Lt. Elf had a major crush on Captain Tagon, a crush that was obvious to every member of the crew except Tagon. (Pretty much every attempt by Elf to broach the subject was interpreted by the one-track minded - and occasionally stunningly dense - Tagon as referring to their current mercenary job). She eventually gives up on Tagon and hooks up with Second-In-Command and company Mad Scientist, Kevyn.
In Shinigami Death Punch, Purple remains completely oblivious to White's feelings despite increasingly obvious signs. He's also oblivious to Blue's blatant come-ons, a source of eternal frustration for White.
The relationship between Marik and Yami Bakura/Florence in Yu-Gi-Oh! The Abridged Series could be seen as this, in an entirely non-serious way (of course). Marik is implied to be gay but oblivious to it throughout the series, and completely fails to understand when Bakura hits on him, leading to many sarcastic comments on Bakura's end. Then, out of nowhere in a bonus video, when Marik is trying to get Bakura to sing Come Sail Away by Styx by offering him things like killing Yugi and giving him his Millenium Rod, he suddenly says "What if I told you I loved you?" Cue shock from Bakura. Then they sing together to the end of the episode. It's actually kind of adorable.
Parodied in Girlchan In Paradise (along with everything else). Girlchan is in love with Yusuke and thinks that he is "incapable of love due to his dark and brooding past". Episode 3 implies that he is fully capable of love... he just despises Girlchan.
In the you could make a life universe, David is oblivious to his feelings for Jake (though it's more a case of willful denial, since Jake is the always-better-than-him rival he's "supposed" to hate). He also fails to realize that Jake is doing his best to date him in between their bouts of sex.
From another story in the universe, Andy is painfully oblivious to the fact that his crush on Derek isn't unrequited to the point where the only reason it takes them seven whole chapters to get together is that Andy keeps running away from Derek whenever they end up in bed together which causes Derek to assume that he doesn't feel the same after all, etc, etc.
Parodied in The Nostalgia Critic's fourth video about commercials, which has a Running Gag about a witch who wants to have a sexy time with someone. She attempts to tell her targets about it via all sorts of innuendos, and when that fails, she resorts to bluntly spelling it out to them. They remain utterly oblivious even then.
Happened to an absurd amount in Clone High, with Abe completely oblivious to Joan's feelings until the final episode. When he realizes he loves her, he proceeds to ask Gandhi whether his feelings could be reciprocated. This causes 1. a flashback showing all the extremely obvious hints seen so far and 2. Gandhi slapping him in the face.
Abe: ...I see.
In Thundarr the Barbarian, Ariel is clearly in love with the titular barbarian and he has no idea whatsoever. His reactions to her are strictly due to friendship (and chauvinism).
In Hey Arnold!, Arnold completely fails to realize that Helga is deeply in love with him (although the fact that she can only express it through insults may have something to do with it). And this does not even begin to describe how utterly dense Arnold is. In the episode Girl Trouble, Arnold's grandpa literally spells it out for Arnold, explaining all of Helga's behavior perfectly and even adds in a story about how Arnold's grandma was the same way at that age. Granted, his grandparents are old and pretty kooky. Furthermore, it sounds ridiculous that someone would antagonize because they like you at face value. She finally confesses to him and the issue would have been resolved in the Jungle Movie.
In the final episode of Braceface, Sharon is oblivious to Alden's feelings for her to the point where it's ridiculous.
Road Rovers: Hunter, it is hinted at throughout the series, but in the last episode it is made quite obvious that Colleen has a crush on Hunter. She asks him if he would like to go for walk on beach to which he responds with an enthusiastic "You bet!" Cut to Hunter as a regular dog with Colleen holding his leash.
Colleen: "Not exactly what I had in mind."
On Phineas and Ferb, Phineas manages to remain completely oblivious to Isabella's feelings for him. It's a particularly bad case, since Isabella is not particularly subtle about her crush.
For example, she once does this◊. He still doesn't get it.
Turned Up to Eleven in the "Summer Belongs to You" double-length episode, where Phineas can notice the obvious attraction of all the OTHER couples around him, but the notion of him going on a romantic date with Isabella, in Paris, shortly after she finishes singing an adorable song about her affections (In a show known for leaning on the fourth wall) is completely alien to him, causing Isabella to grow increasingly aggravated.
Also deconstructed. He was raised by a tough love dad (later revealed to not be his dad, but was taken from his birth parents. He did a better job than birth parents and all of this was due to the machinations of the Nibiru entity.) His dad raised to be a typical manly-man with little focus on feelings. It takes him a while to come to terms with her liking him and him liking her.
Perhaps subverted in episode 24. They finally kiss and Fred apparently proposes to Daphne, although his phrasing is either a metaphor for marriage or a certification for van seating arrangements (Daphne and/or Velma are always riding shotgun).
Although one episode ended with him giving her a Longing Look...
"Hey Gonard. I just realized something. Suki's a girl."
In The Boondocks, it is hinted that Jazmine has a crush on Huey. However, Huey seems to be oblivious to her feelings due to him focusing on social and political issues.
In Kim Possible, Ron apparently never realized that Tara or Yori liked him.
In SWAT Kats, Jake/Razor doesn't seem to realize Callie's feelings towards him. (Doubly hilarious in that he and Chance/T-Bone have competed for her attention in the past.)
Lampshaded in Justice League Unlimited, in the episode "Kid's Stuff" where Green Lantern, Superman, Wonder Woman and Batman are changed into kids. During the episode Wonder Woman is clearly showing her attraction to Batman, who seems to be too embarrassed to acknowledge it, where as Superman is completely oblivious to this
Kid Green Lantern: (to an oblivious Kid Superman) Man, for somebody with, like, fifty different kinds of vision, you are so blind.
Kid Superman: ... what?
In the Earthworm Jim TV series, it's uncertain if Princess Whats-Her-Name is this due to her childhood as a self-taught rebel against her evil tyrant of a sister, or if she reacts with confusion (and a hint of irritation) whenever Jim goes on about their relationship because she isn't into him in that way, has never given him any sign that she was interested, and he keeps on insisting they are boyfriend and girlfriend because he's basically a Cloud Cuckoo Lander.
At the end of "Secret of My Excess", when Spike & Rarity are (seemingly) plummeting to their deaths, Spike starts to confess to her... only for Rarity to stop him and give a tearful smile, heavily implying that she already knows. Extended universe material does show she seems to underestimate his feelings for her though, as his love for her was what finally broke the Nightmare curse on her along with the friendship she had with her friends.
In The Simpsons episode "Colonel Homer", Homer becomes the manager of an upcoming country singer, Lurleen Lumpkin. He fails to notice that Lurleen is in love with him, even when she invites him to her trailer, and sings the highly suggestive song "Bunk with me Tonight" for him:
Homer: Oh, that's hot. There isn't a man alive who wouldn't get turned on by that. (stands up) Well, goodbye!
Alternately, he may know, but he's happily married and doesn't wanna hurt her feelings.
When it comes to Kid Flash/Artemis, Everyone Can See It...except them. There's hints that Kid Flash is aware he's attracted to Artemis, but won't pursue her due to her replacing one of his friends. Artemis takes a while to realize her own feelings.
Miss Martian doesn't really catch on to Superboy's affection for her until he kisses her.
In a (possibly) platonic version, Blue Beetle seems oblivious to just how interested Impulse is in him. It's because Bart's whole purpose for being there is to stop Blue from making a Face-Heel Turn and destroying the Earth.
If you don't think that it's possible for this to happen in real life, just look at these seven reddit threads: