Yuru-Yuri: Sakurako becomes the very definition of this when Himawari spends time after school teaching Chinatsu to knit a scarf for Valentine's day instead of tutoring Sakurako. If this weren't a typical comedy anime, the episode probably would have ended with them becoming an Official Couple.
Semimaru towards Ango in 7 Seeds. He already wasn't absolutely okay with him, but when Ango began helping Natsu, Semimaru really began to hate the guy because Natsu is his.
Also, Momiji points out to Kyo that some other man might marry Tohru if he doesn't overcome his feelings and get her, in order to inspire him. Indeed, when the new school year begins, he overhears some classmates discussing that she's pretty, looks dumb and easy to seduce; this inspires him to walk over to her and look possessive, to drive them off.
In the anime, one movie, and an OVA, Sakura is inexplicably jealous of any girl that takes Naruto's attention away from her even though she constantly claimed in Part 1 she didn't even like him. This was also seen at least once or twice in Naruto Shippuden.
Additionally, Sasuke grows jealous when he discovers that Naruto is advancing faster than he is, eventually completely annihilating his better judgment and going off to join Orochimaru. It just goes downhill from there.
This jealousy was spurred on by another bout of jealousy. Sasuke was jealous that Itachi had focused his attention on Naruto rather than him, even if that attention was entirely negative. This spurred him into fighting Naruto, which revealed the difference in their strength.
Naruto was jealous of Sasuke long before Sasuke was jealous of him, however; both for his skills as a shinobi, and because Sakura was a Sasuke fangirl, while she disliked Naruto. One of Naruto's primary motivations early on in the series was to show up Sasuke and win Sakura's affections.
Lee gets jealous of Naruto and Sasuke despite having curbstomped both of them; the former for defeating his rival Neji, and the latter for getting to fight Gaara in the finals and having theSharingan.
In Skip Beat!, this is explicitly shown as the reason Kyouko didn't have any female friends back in elementary or junior high school: since she was too close to School Idol Shou, the other girls outcasted her. Several other characters in the series have this as part of their personalities: Shou towards Ren, that Rich Bitch against Kanae, a certain band leader toward Shou...
SHUFFLE!: Kaede directed towards Rin. More so than the other characters of Rin's harem, anyway.
Nadia: The Secret of Blue Water: During the Nautilus episodes, a triangle of jealousy emerges between Grandis, Electra, and Nadia... for different reasons. Grandis is jealous of Electra's love for Nemo. Electra is jealous of both Grandis's attraction to Nemo and Nadia out of her own fear of losing Nemo (she tries to suppress it, though). Nadia, meanwhile, becomes jealous of Jean's friendship with Electra, to the point where she fears she may lose him to the latter (when in fact, nothing romantic is happening between either). Even Sanson is somewhat implied to be jealous of Captain Nemo at one point... although partially out of fear for Grandis' usual amorous fickleness and failed love affairs.
In Lovely Complex Otani was jealous when Risa had a crush on Maity sensei, leading him to realize/confess his feelings. Later, he is also jealous and possessive towards Risa on several other occasions. To say nothing of Risa, to a lesser extent, over Otani as well. Then there's Mimi who is a Yandere over Otani. She gets better, though.
In Kekkaishi, Yoshimori is jealous of Tokine always paying attention to his older brother. Also Tokine was seen obviously jealous when Julia was crushing on Yoshimori.
Sailor Moon: Usagi towards any girl who expresses interest in Mamoru. Queen Beryl, Galaxia, the anime's Ann, and Nehellenia are jealous of Usagi because of her romantic involvement with Mamoru. Then there's the anime's Ali and Prince Diamond, who are both jealous, to a T, of Mamoru. Finally, Zoisite is quite a literal example where Kunzite's concerned, getting offended anytime Kunzite shows affection or attraction to anyone who isn't him.
Black Cat: Train + Saya = An insanely jealous Creed.
Full Metal Panic!: Ditto with Gauron, only it's Sousuke + Kaname = One very pissed off Gauron. It doesn't even have to be with Kaname. Sousuke + anyone else (including True Companions / father figure) = very pissed off Gauron. As far as Gauron is concerned, Kashim should not be with anyone else.
Yui in Fushigi Yuugi is jealous of both Tamahome and Miaka, constantly trying to come between them.
Peach Girl revolves around this Trope. Let's see...
Sae is jealous of Momo to the point of hating her, but she possibly admires her as well, otherwise she wouldn't fuck with Momo's life so much, and try to steal Toji away from her. Toji and Kairi are also jealous of eachother because they both are competing for Momo's attention.
In Daa! Daa! Daa! Miyu has been jealous of Kanata's old childhood friend, and Kanata jealous of that older guy Miyu had a crush on.
In Magic Kaito Kaito was jealous that Aoko felt safe with the teacher while they were exploring the school after dark and that she didn't partner with him and that she didn't seem bothered by Hakuba asking her out.
In Detective Conan Shinichi felt jealous when it seemed any male was interested in Ran, Heiji has been jealous of a magician when Kazuha flirted with him, Kazuha jealous of Ran when she thought Heiji liked her and several other characters showing jealousy.
In Love Roma Hoshino has been jealous of Negishi's old classmate.
In The Familiar of Zero both Louise and Saito have shown IMMENSE jealousy whenever the other showed interest in anyone but them (especially Louise).
In Revolutionary Girl Utena:, the very green-haired Kyouichi Saionji is the personification of envy. He's envious of his best friend and classmate Touga because he seems to be better than him on every field, he's envious of the chairman Akio because, well, because he's the fat cat, and he's envious of Utena because hey, she defeated him, she got Anthy as her "bride" and she's now the "official" Prince... on second thought, poor guy. Okay, maybe his eyes aren't green, but he has a "green" theme going on (hair, pants, duelist rose).
This is also Shiori's motivation. She felt inferior compared to Juri, so she began hanging out with her to manipulate her feelings, culminating in stealing a boy who wanted to ask Juri out. The real tragedy is that this worked and turned Juri into a Broken Bird...because she was in love withShiori from the start.
In Tokyo Crazy Paradise both Ryuji and (eventually) Tsukasa have been jealous when the other showed any interest in anyone but them.
In The Prince of Tennis, Tomoka's jealousy of almost any girl who talks to Ryoma (aside of Sakuno), Kamio's jealousy of any males who get too close to his crush An, and Yuuji's possessiveness of his partner Koharu are quite played for laughs. In the manga, Sakuno also has a brief moment of jealousy when Kotoha from Tsubakikawa appears and claims to be in love with Ryoma, but unlike the others she manages to set it aside.
Yuuta Fuji's jealousy of his older brother Shuusuke and Kurumi Iijyuin's jealousy of her older twin sister Narumi make both of them rebel against their more succesful siblings. A big part of Shuusuke's earlier Character Development is tied to him first hiding his own pain and later managing to resolve the issue with Yuuta; later, he uses his experience to help Kurumi reconcile with Narumi.
Takuma Fudou from Get Backers is shown to be this... and not towards Ban, but towards Ginji. To elaborate, he's jealous of the attention that Ginji gets from Ban, and he actually tells Ginji that he dislikes him because Ban doesn't even notice him when Ginji is around. He then proceeds to try to Murder the Hypotenuse while telling Ginji that Ban's eyes aren't on him because Ginji is in the way.
In the live-action adaptation of Uzumaki, it's Mitsuru, one of Kirie's schoolmates, who becomes this. He practically makes deep gouges on the tree he's hiding behind while watching Kirie and Shuichi, and the look on his face is that of sheer jealousy and hatred towards Shuichi.
This is why Natsume from Hidamari Sketch is often such a jerk to Sae: on the day on the entrance ceremony, she found herself having to go alone, the train (which normally takes 42 minutes on top of the 10 minutes by bicycle) had to make an emergency stop, she took the wrong street, and finally, she found the shoe locker she thought was hers to be full. Sae directed her to the next set of lockers, and they talked as they hurried. Now, Natsume latched on to this, thinking that they might become best friends. She was unable to meet up with Sae, and didn't see her until ten days later, and upon greeting her, found her with Hiro, who was in the same class and apartment. This triggered something inside her, and, well... she realized as she sulked after her initial outburst that Sae didn't do anything wrong, but that didn't prompt her to change. (As a side note, Natsume does have green eyes.)
In Strawberry Marshmallow, Miu often feels jealousy over Nobue's preferential treatment of Ana and Matsuri, and sometimes competes for her attention even when she's trying to take care of her sister when she has a cold.
Wendy Garret of GUN×SWORD displays jealousy whenever other women show too much interest in Van. (She's also green-eyed, but that's probably a coincidence!) It is just possible that some of Van's dislike of Joshua also falls into this trope, but that may be a stretch.
Touma's mother looks really scary whenever her husband looks at another woman.
Every member of Touma's harem gets angry when they see him with another girl.
Accelerator and Hamazura's harems get mad when they see the two hang out with Fremea, even though she's only a little girl.
Tekkaman Blade: Tekkaman Evil/Shinya is loved by his family, but feels like he's being considered the weak one as the 'good' treatments was given to Blade/Takaya, for instance, when they both were nearly drowning, Shinya was saved instantly, but Takaya was told to just save himself... yet Shinya was JEALOUS because the family trusted Takaya's strength over his own strength. Kind of complicated, yes.
First, pre-Eclipse Griffith grows quickly jealous when he notices that Guts and Casca have become an item. It is unclear who he envies more due to his ambiguous sexual orientation. It's possibly both.
Averted with Judeau. Despite his unrequited crush on Casca, he knows he has no chance whatsoever, noticing the bound she and Guts had formed, even before either of them would realize it. Preferring to lose with honour, he helps a lot in the cementing of Guts and Casca's relationship, even going as far as encouraging Guts to take Casca away with him, by force if necessary.
During the Griffith rescue operation, Casca had the Green-Eyed Monster attitude toward Princess Charlotte for a bit, since she admitted that she was still worshiping Griffith like before, even after she and Guts made love for the first time earlier. She tried reconciling to herself, but ended up saying the wrong thing to Guts about the matter, which succeeded in pissing Guts off even though HE admitted to himself that he couldn't take his mind off Griffith. But don't worry - they made up later.
Then, post-Eclipse, there's the unspoken rivalry between Sonia and Charlotte. Charlotte is Griffith's Meal Ticket, even though he acts in order to make her feel like he actually values her for herself and NOT her birthright. Sonia is a faithful servant to Griffith, gifted with clairvoyance, and as such considers herself the only girl worthy of him. Sonia is very jealous of Charlotte but her nascent and reciprocated relationship with Irvine might wash it all out.
There's also the jealousy Farnese feels for Casca for being the object of Guts's affection. Farnese is technically betrothed to Roderick, who is himself quite handsome, but she definitely has a crush on Guts who doesn't see her beyond being Casca's caretaker. Farnese even breaks down in front of Casca, telling her that she's really ungrateful to ignore Guts after all he did for her but Casca being insane and regressed to infancy, it doesn't really do anything, although Casca seems to understand Farnese's distress.
Finally, there's Schierke's Precocious Crush on Guts but, unlike Farnese, Schierke only has shades of this and knows deep down that she's way too young for Guts (he is more than twice her age). Plus, her Toy Ship moments with Isidro also seem to drop some hints about she may eventually like.
In the manga of Brigadoon: Marin and Melan, one of the first signs that Melan is developing romantic feelings for Marin is the jealousy or anxiety he displays when he sees her alone (and half-dressed) with another love interest.
Soul Eater has the Envy chapter of the Book of Eibon, although we only see what Soul and Maka have envy for; Maka is jealous of Liz and of music itself, since Soul loves it so much while she can't even understand it, despite studying it ad nauseum. She's also jealous of/worried about other meisters who claim to fit Soul better - especially girls. Soul is jealous of his older brother, Wes, for his superior musical talent. It is also implied that he chose to be Maka's partner because she didn't understand music, and he feels guilty for that. What makes this even better is that Maka actually has green eyes.
Madame Red in Black Butler. The love of her life Earl Phantomhive (Ciel's father) married her beloved sister. She tried to be happy for them but when Ciel was born, jealousy started to consume her. Even when Ciel's parents died in the fire, though devastated, she envied her sister for dying with someone she loves.
Vegeta from Dragon Ball Z has got to be the epitome of this trope. Throughout the entire series Vegeta envies Goku because no matter how hard he trains and fights he is never able to surpass Goku. This becomes a literal case of Green-Eyed Monster when Vegeta becomes a Super Saiyan (the transformation gives you green eyes) and despite finally becoming the warrior of legend that the Saiyan Race had admired for thousands of years in reality, still couldn't let go of his pride. During the era of peace after Goku died he still finds a reason to be jealous because he sees that Goku's family life is more loving and meaningful than his is as Goku's family supported him and made him a better fighter while his didn't show the same results. It is only when Vegeta lets go and admits that becoming better than Goku isn't all there is to his life that he truly shines as a warrior and becomes a good guy.
Bleach: After Ichigo sinks into depression because his failure to protect resulted in his friends getting badly injured, Orihime can't cheer him but Rukia does by making him resolved to never let any of his True Companions get that injured again. Orihime believes she's incapable of bringing Ichigo out of despair leading her to feel jealous of Rukia's ability which has made her feel useless. This trope is immediately subverted when, instead of becoming bitchy or bitter, Orihime gushes about how wonderful and amazing Rukia is and how bad she feels to be jealous of such a good person. Rangiku resolves the issue almost immediately for her and a few chapters later it's confirmed Rukia and Orihime are very good friends and training hard together.
Captain Brian, Lostman's superior in the Navy in Moonlight Mile. Annoyed at being repeatedly shown up by Lostman, he intercepts the orders for him to be transferred to NASA, refusing to release him from his command without flying one last mission for him, stating that while flying the Shuttle is more honorable than flying fighter jets, until the orders go through, Lostman is still a soldier, and a soldier's highest duty is to risk his life for his country. Then he lets Lostman get shot down. Lostman's lost behind enemy lines for over a year before he comes back, by which time he's joined NASA... and Lostman ends up his SUPERIOR.
In Candy Candy, Annie Brighton confesses to Candy White Andree, during an emotional breakdown, that she has always been secretly jealous of her. This is because Annie is a Fragile Flower who is very scared of reaching out to others, whereas Candy is a fearless Plucky Girl who always reaches to the rest — even in the times when they were heartwarming orphans, Annie always felt less appreciared and loved than Candy was. It's really not helped when the boy that Annie likes, Archie, says that despite caring for Annie, he likes Candy as well. (Partially because he is jealous of her other current love interest, Terry).
In Kase-san, Yamada regularly feels dispirited at the thought of Kase's many admirers and feels jealousy at the thought of Kase potentially having already dated a girl before her.
Is the Order a Rabbit?: Just a very subtle one, but in episode 6, Chino feels left out when her two school friends, Megu and Maya, spend a lot of time with Cocoa and Rize at the Rabbit House. When she tells Chiya about it, the latter notices the former is unaware of the feeling of loneliness when she saw all of them like that.
Salia in Cross Ange is this towards Ange, particularly Ange being the pilot of Vilkiss instead of her but this is more because Vilkiss used to be her commander's unit and that she really wants to use it, going as far as switching from her Para-mail to Vilkiss while Ange wasn't around. She does get over it in the same episode when she finally witnesses that Ange is the only one capable of unleashing Vilkiss' full power.
Salia isn't alone in the Ange envy - Julio had her beaten to the punch ages ago. He'd been envious of the preferential treatment her sister received, both from their mother and as the public favorite for empress, so he exposed her as a norma leading to her disgrace and current predicament.
Attack on Titan: Jean, who maintains a rivalry with Eren because of his crush on Mikasa.
First off, we have Yamano Taishou who is a strange case. At first Taishou is jealous of Buchi because Buchi was getting so much praise in school. Then he gets jealous of him when he learns that his foreskin has pulled back, while his own foreskin hasn't pulled back because he has phimosis. He was going to embarrass Buchi by taking nude pictures of him and releasing them at the school, but when he sees an old picture from when he first met Buchi, he decides to not release them.
Then in the second volume, Taishou grew jealous of Buchi because he was working on a school project with Fukami, even though he really wanted to work with Buchi. It doesn't help that Taishou and Fukami never had much of a strong friendship so Taishou didn't like Fukami much. When Buchi tells Taishou that he is his friend just like Fukami, Taishou felt that Buchi was comparing him to Fukami which got Taishou really upset. It results in Taishou raping Buchi due to Taishou taking out his envy of Fukami on Buchi. Fukami discovers what happened and he punches Taishou to get him to stop. When Taishou finally realizes that he raped Buchi, he immediately regrets it and breaks down crying.
Then we have Amanuma Shinichi who is quite an extreme example.
First he was jealous at the fact that when he got into a top middle school, that he wasn't a top student like he was in elementary school which led to him dropping out of that school and temporarily becoming a Hikikomori.
When he became a Hikikomori, he pretty much became jealous of everyone because so many people thought that he would be a top student in a top middle school, but instead he ended up dropping out of middle school and he felt that everyone around him saw him as a failure. He even felt that his own parents saw him as a failure.
When he transferred to Buchi's and Taishou's middle school, he became jealous of Taishou because back in first grade, he bullied him a lot and he thought that it would have affected him a lot in middle school. But he was surprised to see that Taishou was just about an average middle school student, while he had everything that happened to him.
Tokyo Ghoul: Kanae seems to harbor an intense jealousy towards Chie and Sasaki, simply for having Tsukiyama's interest.
In Kumo Desu Ga, Nani Ka? Sophia was envious of Wakaba Hiiro in her first life for being beautiful and stand-offish without being ostracized like her. In her second life she becomes envious of Shiraori for her strength, which extends to anyone stronger than her and eventually results in her developing the EnvyRuler skill.
Pokémon: The instincts of wild Pokemon drive them to fight over food sources, territory, mates, etc. But wild Pokemon often attack domesticated Pokemon out of nothing more than jealousy. Given that the latter get 24-hour healing, food and protection for doing nothing other than what all Pokemon do naturally- fight- it's not hard to see why.