When two characters are shipped together, in canonorfanon, despite the huge power issues that their relationship features. They can be a boss and their employee, a lord and their vassal, a mentor and their student, etc., but one of the characters is in a position of greater influence over the other one.
Shippers either blissfully ignore the implication of the unequal power balance, or they fetishize it. The idea of devotion to the most powerful member (and vice versa) may be frequently mined (often with a version of the Bodyguard Crush or of the Subordinate Excuse). The power dynamic may also be subverted by showing other ways that the least powerful character actually holds status. It's frequently the less powerful character who is shown to be the initiator of the relationship, which reduces the potential Squick factor somewhat by demonstrating that they aren't being coerced.
Teacher/Student Romance, Mentor Ship, Parental Incest, Bodyguard Crush, and A Match Made in Stockholm are subtropes of this. The probable, albeit frequently-ignored, result of Wife Husbandry.
One Piece has Nami/Sanji. Nami likes to bend people to her will. Sanji won't say no to a girl. You take it from there. Most of the time it ends up fetishized.
Also in fanon, the domineering Smoker and his subordinate/protegee Tashigi. (Though in canon, it's probably more of a father/daughter or teacher/student relationship.)
And Luffy/Boa, but not in the way you'd normally expect looking at their age differences. She's canonically hopelessly in love with him and would do anything he'd ask (on top of believing they're already in a relationship), while he sees her as a friend who helps him rescue his older brother.
Cardcaptor Sakura features several canon examples of those, such as Kaho/Touya, Terada/Rika and Clow/Yue.
Lyrical Nanoha has Hayate/Vita. They hit this trope more than once, and both ways. In one direction, it's a case of master/knight (within their personal sub-group) and superior/subordinate officer (within the military they joined). In the other direction, Hayate is 9 years old (25 by the fourth season), while Vita has been around for centuries (but looks young enough to be a first-grader).
Then again, Hayate sees the Wolkenritter as family rather than servants, and Vita seems to be the least inclined of the Wolkenritter to view Hayate as a mistress- note that she doesn't add any honorifics to Hayate's name and rarely speaks of her as her mistress.
At some point during Chrono and Amy's relationship, Chrono was captain of the same ship Amy was serving on, but by the time they get married, Amy has retired from the TSAB.
Kazuki in Get Backers is most frequently shipped with such characters. Just about everyone in his Backstory is slavishly devoted to him and acts like he left them at the altar when they reappear in the story proper. Juubei, Toshiki and Saizou were all his subordinates in their gang, Fuuga—which was started mainly as a way to gather protection around him. More specifically, his childhood friend, Juubei's, family has been allied to Kazuki's since time immemorial, and the male heirs of their families are traditionally a lord and his physician. Plus there's Ren, a thirteen-year-old girl who admires twenty-year-old Kazuki as he was a high-ranking member of the VOLTS gang, and just that charismatic when she actually met him face to face. Sakura, Juubei's sister, the Team Mom who turns Fuuga into a Five-Man Band, is probably the only one who doesn't act madly in love with him—and it was she who noted that no matter what happens, they will always be bound to Kazuki and always be there to protect him. For his part, Kazuki cherishes them all and repeatedly refuses to accept it when the thin line between love and hate turns them against him, or each other.
And Alucard/Integra too - although the fact that he's her servant is somewhat offset by his age, power and willful personality (not that his master lacks in the latter department...)
While Roy Mustang and Riza Hawkeye in Fullmetal Alchemist know each other from childhood, the fact is that he's a few ranks her superior in the current story. She calls him "Sir" or "Colonel". He calls her "Lieutenant".
There's also Ling and Lan Fan, who are possibly even more unequal, with Ling being the twelfth prince of Xing and Lan Fan being his bodyguard, and from a family that has served his for generations. Ling doesn't really seem to care about the differences in rank, while Lan Fan appears to be very dedicated to her duty; naturally, fans treat this approximately the same way a person dying of thirst might treat a glass of water.
Then there are Roy/Ed shippers. While the difference in their ranks is not as great as with Royai (since all State Alchemists start out as Majors, and Ed usually doesn't give a damn about rank anyway), Ed's age adds to the inequality.
While they never actually become an Official Couple, Code Geass plays with this trope regarding Kallen and her Bodyguard Crush towards Lelouch. However, the one time that this trope is actually invoked is when Lelouch tries to force his attentions on Kallen under the pretext of needing "comfort"; this ends with Kallen slapping him. The event marks the turning point in their relationship where Kallen stops being a fangirl and becomes a full-on Love Interest (let's be clear, it's obvious she would have said "yes" any time he'd ask her in a less insulting way).
According to the official guidebook, Lelouch considered only four people his equals: his father, Schneizel, C.C. and Suzaku. Unless you ship him with one of those (and to be fair, Lelouch/C.C. and Suzaku/Lelouch are very popular pairings), any Lelouch ship is almost unequal by definition. Which is probably one of the reasons Lelouch stays celibate.
When you get down to it there are a lot of unequal pairings, mainly because the Code Geass writers love the whole Bodyguard Crush scenario (and using royalty and their knights) - apart from Lelouch and Kallen as mentioned, there's Suzaku/Euphemia (canon), Guilford/Cornelia (pretty much canon), Schneizel/Kanon (arguably canon) and Charles and Marianne (canon in the backstory). And Lelouch/Suzaku if you see it that way.
Interestingly enough, in Nightmare Of Nunnally, Charles begins falling in love with Marianne after she calls him out on the amount of bloodshed in his quest to secure power and he is influenced by her ideals.
In Suzumiya Haruhi, Haruhi seems to really want to get into a relationship with Kyon, who is actively involved in a team effort to keep her in the dark about her true nature as aReality Warper of inmense power. If Kyon were to reveal the secrets to her, however, it would not equalize them, but rather put her clearly above him.
But of course keeping Haruhi and, by extension, said power in check involves going along with all her crazy schemes and letting her believe she's in a level above anyway, and going along with it when she pulls rank.
Kyon and Yuki is also rather unequal, given that Kyon is a normal human (as far as we know), whereas Yuki is an alien who won the Superpower Lottery several times over.
In Full Metal Panic, Captain Teletha "Tessa" Testarossa's Unrequited Love for Sergeant Sousuke Sagara is doomed mostly by this trope; because she is his commanding officer, Sousuke can't bring himself to reciprocate her feelings. Fan pairings of Sousuke with basically anyone else from Mithril, such as Commander Andrei Kalinin and Lieutenant Benjamin Clouseau, are subject to the same inequality.
There's also Melissa Mao and Kurz Weber; the less dramatic inequality in their ranks is made more significant by the fact that Mao is Sousuke and Kurz's team leader - a fact which Kurz mostly ignores and which isn't really addressed since Kurz is killed in action not long after the two of them begin their relationship.
Mao tries to enforce this, but once Kurtz is discovered to be alive, Mithril is all but dissolved and there is no need for rank anyway.
In Katekyo Hitman Reborn!, there's the pairing of Gokudera and Tsuna. Tsuna is the current boss of the Vongola Family, and Gokudera is his incredibly loyal underling and wannabe right-hand man. Fangirlslove the dynamic of their position and status difference. And despite Gokudera being the one who is most self conscious about the difference in position, he's always the aggressive one that tops.
Naruto. This is a common issue for the Neji/Hinata pairing, as Hinata is heir to the Hyuga clan while Neji is a branch house member whose duty is to protect and serve the main family. In some fan fics, the common application for the trope is inverted, with Neji becoming head of the clan and Hinata being demoted to the branch family.
It's made even more obvious when it's revealed in episode 232 that Neji has also become Hinata's mentor and trainer, when Hinata requested him to be, not long after his Heel Face Turn.
A Running Gag in the Pokémon fandom is that no matter who he's shipped with (with the possible exception of May), Ash Ketchum will always, always be on the bottom.
Death Note has the 'ship of Light/Mikami, "God" and his servant.
And, of course, the canon ships of Light/Misa and Light/Takada. God and his two devoted slave girls (the fact that he isn't doing it because he likes them is beside the point).
Interestingly enough when Light gets shipped in Fanonit's frequently unequal theother way. This trope almost always comes into play when shipping him with L-an older man who controls the world's police and has the authority to have him sentenced to death if he says no. Also with the canon Light/Misa ship-especially early on when she essentially forces him to be her boyfriend under implied threat of death.
It should be also noted that Misa is older than Light by a couple of years (not much, but she is still going out with a teenager while she is in her twenties).
The pairing of twin brothers Agon and Unsui from Eyeshield 21 has this subtext as one of the reasons fangirls LIKE them as a couple.
To explain, Agon enjoys nothing more then exerting power and superiority over others and in general, is quite sadistic. Unsui, the kinder but weaker twin, wants his brother to live to his full potential and be the best. This is flanderized in the anime, where Agon is made even more violent and Unsui flat out states he only exists to serve his brother. Needless to say, it doesn't take much effort to imagine their relationship as another extension of Agon's sadism.
Pick an Axis Powers Hetalia pairing, ANY pairing where one member used to raise/oversee/rule over the other. It doesn't matter if they've actually received canonical hints or not; there WILL be shippers for it. Sometimes they'll set their fanworks in a time period where the characters' statuses are more equal, but many other times they won't.
One canon example is the Official Couple of Finland and Sweden. Their relationship became equal at some point, but it started off with Sweden running off with Finland and insisting that Finland was now his wife, while Finland was still too afraid of Sweden to stand up to him.
Tenshi Ni Narumon: Raphael and Mikael are teacher and student respectively although at the end of the series Mikael kinda ended being promoted to a teacher himself - but he still uses a highly respectful "sama" when talking to Raphael.
Taki and Klaus from Hyakujitsu No Bara. Taki is a Division Commander, and Klaus his knight. In military situations, Taki is clearly in command. It's a different scenario otherwise...
Pairings in Sekaiichi Hatsukoi revolve around a worker in the manga industry and someone with more authority.
Quite a few Yu-Gi-Oh! fans ship Kaiba and Jonouchitogether. This has a few problems. The first if that Kaiba's a teen genius who's incredibly wealthy and has a lot of influence, while Jonouchi barely makes enough to get by, so socially, Kaiba far outranks him. Kaiba's also much smarter, stronger, and a better duelist than Jonouchi. Adding it all up, it basically means that Jonouchi would be Kaiba's bitch, whether he likes it or not - several fanfics actually have it that Jonouchi lives in Kaiba's mansion, which further adds to the unfairness of the ship as it makes Kaiba his landlord as well. A lot of fans fetishize this, giving them a VERY unequal Master-Servant style relationship.
In Watchmen, the immortal quantum-being Doctor Manhattan pairs up with the completely human Silk Spectre II.
Fan Fiction
Played very interestingly in Dungeon Keeper Ami. On one hand, Ami is Jadeite's employer- in the DungeonKeeper universe, this basically amounts to indentured servitude, sometimes outright slavery -and it is not at all uncommon for Keepers to have such relationships with their 'Property'. On the other hand, Ami is extremely uncomfortable with the associated implications. Interestingly, or worryingly, Jadeite is surprised when he finds out, as in the Dark Kingdom a superior would not hesitate to use their power over subordinates. Their positions are reversed later, when Jadeite starts teaching Ami Dark Kingdom style magic, he reciprocates her tact.
Films — Live-Action
Pairings of Jedi Masters with their Padawans are popular in the Star Wars fandom, especially Qui-Gon/Obi-Wan and Obi-Wan/Anakin. (As Masters are responsible for their Padawan's upbringing, at least part of the way, this also counts as Wife Husbandry.)
Though less drastic as other examples here, power dynamics are possibly the reason there's as much slash fic for Eastern Promises as there is.
The American President makes one of these its main plot, exploring it from several different angles. As you might guess, one participant is the President, and the other is an ordinary woman of no special fame or fortune.
A sizeable chunk of the fandom for Tim Burton's Alice in Wonderland ships the Mad Hatter with the White Queen, rather than Alice. Bear in mind that these two characters never actually speak to each other onscreen in the movie. They point out that the two have known each other for a long time (he had been her court hatter), they're the only ones who survived the Horunvendush Day attack, and they are staunch allies even if they're not shown talking. They're also the same species, which helps.
Literature
Harry Potter has many popular ships of the teacher/student kinds, with Snape/Hermione and Snape/Harry as their most popular. In the fandom, these are referred to as "cross-generational pairings." Many of them make fans quite squicked.
Voldemort and Bellatrix, his "most faithful" servant.
A non-fanon example occurs in David Edding's Belgariad. After Durnik's death, Polgara announces that she loves him. However, while Aldur helps him return, he informs Polgara that the fact that she's a sorceress and Durnik's not would doom their relationship. She agrees to "become his equal" as the price for his return, and for several weeks believes that she's lost her powers — but as it turned out, she didn't. Instead, Durnik had been given power to match hers.
It is also set up and then thoroughly averted with Garion and Ce'Nedra. King Garion is the ruler of Riva and Overlord of the West, as well as being an immortal sorcerer and the designated custodian of a cosmically powerful artifact that can smack down the gods. Princess Ce'Nedra is, outside of a couple extra centuries' of life expectancy via the Dryad side of her family, entirely mortal. Given that under Alorn law, the queen's role is limited to bearing the heirs and being royal chatelaine, this could easily have been one of the most lopsided power dynamics ever seen in a relationship. Fortunately, Garion takes one look at the situation, realizes that keeping Ce'Nedra in that unequal a situation would either crush her spirit or drive her to regicide, and hurriedly writes a 'The queen shall hold powers making her co-ruler to the king and regent of the realm in his absence' into the marriage contract, and then puts it into law.
This set up was, itself, already an aversion of the trope: Ce'Nedra was an Imperial Princess and Garion was, as far as they both knew, a simple Farm Boy. The reveal that he's royalty and that they're betrothed puts them on slightly more of an equal footing.
Also employed in canon in The Elenium, when twentysomething Queen Ehlana marries her middle-aged former bodyguard and surrogate parental figure Sparhawk. This trope concerns Sparhawk a good deal, but he eventually goes along with it. Perhaps the age gap and the authority gap (between sovereign and knight) cancel each other out.
Aes Sedai from the Green Ajah are notorious for having relationships with their Warders. Even weirder, Aes Sedai can actually mind control their Warders, though it is considered a bit unethical.
The real taboo seems to be bonding someone against their will in the first place. The assumption seems to be that once you've agreed to be bonded, you have only yourself to blame.
In Merise's case, all four, at the same time. That is, she had four Warders at the time, not that she... with four... oh hell.
Most relationships in the setting, really, due to the various odd ways the various societies deal with the unusual relevance of gender. In the case of the Sea Folk, who live pretty much entirely on ships with a rigid and extensive hierarchy, it's practically impossible to have relationships not fitting this trope - and they actually make a rule of marriage that the lower-ranked person is in charge in all private matters. A main character discovers this after marrying in one of their ceremonies (she was in a hurry to get married and they were there). Unsurprisingly for the series, she decides she's fine with it.
Note also that it does have the expected consequences; while Cain seems to genuinely love Amberley (and the feeling does seem mutual), he's also well aware that he can't exactly say no to her. Not that unusual in a relationship...except for the mortal combat against countless alien horrors bit.
As Cain puts it in Duty Calls:
I'm sure most of the men in the galaxy are familiar with the sinking feeling that accompanies the words 'Do you think you could do me a little favour, darling?', but when the woman doing the asking is an Inquisitor it's even less wise than usual to say, 'No'.
Actually, given the way 40K's universe is set up, Cain's reputation, and their jobs duties play out, this would actually subvert itself. Cain is the HERO OF THE IMPERIUM, and hooking up with an Inquisitor would not only bolster his image, but Amberly's as well, and given that Commisars and Inquistors tend to clamp down on the same thing (insubordination to the Imperium) and fight the same enemies, it would work. Also, considering that Cain is technically outside the Imperial Guard command structure, and Amberly has the ability to integrate herself into it at any time if it benefits her current assignment, most of the conflicts just seem to die on the vine. Hell, he almost got into a relationship with Regina Kasteen, which would make it unequal on her end, and it can be safely assumed this wouldn't be a major problem. Hell, even Kasteen/Broklaw, another possible ship, would work fairly well, given the above.
For that matter, Grifen and Magot. Grifen is Magot's squad leader but they're still a couple.
Also, Hamish and Honor did not actually start dating until after Honor's promotion to fleet admiral, which put the final nail in their former mentor/protege relationship and made them professional equals. At present, Hamish is again her nominal superior as First Space Lord, but if the Judge Advocate General of the RMN (who was actually consulted) says that their current relationship doesn't violate regs, then it doesn't. Lastly, being 40 years older than someone is less of a gap in a society where the average life expectancy is 250-300 years.
Manticoran regulations say that relationships between different members of the armed services are permissible so long as the people involved aren't in the same chain of command (Thus Honor's relationship with Paul Tankersley, who was one rank junior to her, was acceptable because he was not a member of her crew. If he had been posted to Nike rather than Hancock Station, it would have been a different matter). While being First Space Lord (Civilian head of the Navy) made Hamish technically the head of the chain of command to everyone in the Navy, he had to resign his commission to accept the job. The JAG ruling basically stated that since Hamish was no longer a serving Naval Officer, the fraternization reg did not apply.
In C.J. Cherryh's The Paladin, Master Swordsman Shoka and his peasant-girl student Taizu end up in a relationship, despite the teacher/student power imbalance, their social class imbalance, and the fact that Shoka is just under 40 and Taizu is about sixteen when they meet (although more like 18 when the relationship begins). Things are, in the end, more equal than they sound, because she's far from the passively obedient type.
Also from Cherryh, in the Morgaine series Vanye feared it was literally a sin for him to fall in love with Morgaine, partly because he thought she was qhal and therefore soulless, but also because he was pledged to her service and found that confusing (since normally a warrior could only be pledged to the service of a male noble).
Jeeves/Wooster shippers have to deal with this both ways. On the one hand, Jeeves is employed as Bertie Wooster's valet; on the other hand, though, Bertie is a docile Upper Class Twit while Jeeves is an intelligent, manipulative master of the Batman Gambit.
In A Song of Ice and Fire, Daenerys Targaryne was married off to Khal Drogo for political reasons when she was a destitute, powerless, friendless 13-year-old princess and he was an extremely powerful, feared, 30-something warlord with 50,000 men at his back. Once Dany gained power in her own right, her relationship with her handmaidens became this, as they are her slaves. The shippers love these ships, especially the former.
The shippers also like Sansa/almost every male character, which is basically a guaranteed Unequal Pairing; Sansa has almost no power behind her, aside from being the first daughter of a pretigious family, and she loses that in the first book when her father is executed for being a traitor. Awareness of the inequality in their relationship leads Tyrion to leave it unconsummated, and though Littlefinger is similarly aware, this may not stop him, as he appears to view Sansa as a surrogate for her mother. Which only raises the Squick factor, as he's effectively adopted her as a daughter.
There's also the popular Jaime/Brienne pairing, which can be cut both ways—Jaime is older, more experienced, and a scion of the wealthiest and most powerful family in Westeros and finds it easy to fluster Brienne, but Brienne is larger, stronger, and the better fighter, and likes to call Jaime out on his crap.
Septimus Heap displays much Septimus/Jenna-Shipping despite the fact that canonically a Wizard/Princess relationship is a taboo in the Castle due to the political consequences and rivalry between them.
The Princess Rennsaeler and Jerin Whistler in A Brother's Price. She's several years older than him, while he starts off at just shy of sixteen. This is a world where men are so rare they are almost inevitably sheltered and not socialized to say no, so there's a Questionable Consent situation when they meet. One of Jerin's sisters outlines it.
"She's a princess. All her life people have obeyed her commands. You're a boy. All your life you have listened to others."
This is the plot of perhaps 70 percent of Regency romances, including the genre codifierPride and Prejudice: the courtship between a wealthy aristocrat (usually male) and someone much lower on the social scale (usually female). For good measure, it's not uncommon to add employer/employee dynamics or major differences in age and/or sexual experience. The heroine then proves to the hero by virtue of her smarts and personality that she is actually more his equal than women of his social class.
The scene in which he finds Chloe after Brainiac has wiped her knowledge of Clark's powers and Clark doesn't bother trying to restore the memories, feeling Chloe would be safer that way in Abyss has been under fire for this, especially when it is portrayed as the right thing to do. That being said it lasted a grand total of one episode.
Also, Jason Teague (Smallville High School Football Coach) and Lana Lang (Smallville High School Student). It didn't last long (Teague's status as a teacher, that is) but a Villain of the Week whose motive was enforcing moral values tried to kill him for this. (Jason Teague had long lost the coaching job over this but the villain didn't deem this enough punishment).
In Samurai Sentai Shinkenger, pretty much anyone on the team shipped with Takeru would have overtones of this, since they're all his vassals. The only possibility that could get around it is Takeru/Kaoru, which has its own problems after the results of episode 48.
Buffy the Vampire Slayer fanfic had Giles/Buffy. This is never even suggested in the series, with the exception of a few jokes about how Giles spends all of his time around adolescent girls (and Xander). One character assumed they were together and season 6 had a That Came Out Wrong moment when Buffy claimed she was thinking about Giles when she kissed Spike.
There's also (a lot of) canon Angel/Buffy. Although they both act like clueless fifteen year olds during the time they're in a relationship, Angel is actually over two hundred years old and rarely shares information if he can avoid it.
Season 8 had Xander start a relationship with slayer Temporary Love Interest Renee and Dawn. Giles is assumed to have been Faith's Sugar Daddy at least once.
The Vampire Diaries has Stefan/Elena and Damon/Elena, but both are much older than Elena.
Torchwood has both Jack/Ianto (all the way) and Jack/Gwen (UST) in canon — the fact that the former is the boss to both of them is the least of their worries.
Arguably any pairing of The Doctor and a human (particularly his companions). This is mainly due to the fact that he's a centuries-old Sufficiently Advanced Alien, and the companions are (for the most part) The Watson.
The rather odd Mal/River pairing that pops up often in the Firefly fandom. Not even considering the age difference (Mal is roughly twice as old as River) but he's also the ship's captain, and she's become its pilot, following Wash's death.
There's also the slash pairings, with Mal/Simon and Mal/Jayne.
Mal/Inara also counts. He's a former revolutionary who is now a criminal who does odd (and sometimes illegal) jobs to scrape by. She's a Companion, which means that she's very well-educated, well-bred, and well-versed in reading people and using this to help them feel better. Her job also means that she's considered very high-status as well, to the point where she notes, upon signing up as a passenger on Serenity, that simply hanging around Mal will make him appear credible.
In The Sarah Connor Chronicles, Cameron is programmed to obey John Connor's orders. It hasn't taken the fandom long to extrapolate what John could, would, or has done with an extremelyRidiculously Human Robot.
Unless you're referring to the future John, it's doubtful this qualifies. She's disobeyed the present John at least once, and has stated explicitly that if given a choice between obeying future or present John, she'd choose the future one.
There's also implications of future John Connor/Allison Young, which gets really disturbing when one considers Cameron looks exactly like Allison and can apparently become Allison in personality.
On the other hand, Cameron spends a lot of time around Sarah, and for some reason blithely obeys her every order without question...
Or how about Castiel/Dean? They've been paired together because they act like an astonishingly pretty married couple but, if he wants to stay out of hell and keep his eyes, Dean should probably behave like a good boy from now on.
Kara Thrace and her CO/daddy surrogate Bill Adama. Like that time he risked the entire Fleet to go looking for her after she'd been shot down and presumed dead.
And then there's Laura Roslin/Lee Adama. Again, it's not just the age difference — when they met, he was a hotshot pilot and she was the president. As he put it: "The lady's in charge."
A canon (albeit on-and-off) unequal pairing: Kara and Lee. No age difference, really (okay, Kara's a bit older than Lee), but Kara could take Lee's ass to school any day. And Lee is tough.
The "bible" document for Season One had it that Lee would develop romantic feelings for Roslin.
The main slash pairing of Tour of Duty is Lieutenant Goldman and Sergeant Anderson who are assigned to the same platoon during the Vietnam War.
ITV's The Palace had the King of England and his secretary falling in love, for maximum drama.
In Stargate Atlantis, there's some (not a whole lot, but it exists) fanfic pairing Todd with John Sheppard or Evan Lorne. Question: Which way does the inequality go? Answer: It varies.
Stargate Universe, when it is revealed that Young and TJ not only slept together, but conceived a child in the process.
Picard and Dr. Crusher invoke their differing ranks as a reason why they can't get together. Though, given that Beverly (as the ship's head doctor) could (and occasionally did) pull rank on Picard, that rational feels more like Ship Sinking than characterization. And not that that stopped the fic writers, at any rate.
It didn't stop much of anything, really. In the post-series novels, Picard's gotten over himself and married Beverly.
Also the rank thing was really just a convenient excuse, the real reason is because of Picard's feelings of guilt over the death of Jack, Beverly's husband.
There's also the not unpopular Q/Picard ship. Yes, Picard is captain of the Federation flagship, but Q is an omnipotent, omniscient, immortal alien who can wipe out civilizations with a camp finger snap, so there's not really much of a contest.
This would apply to any hypothetical relationship involving Gibbs/Anyone on Team Gibbs in NCIS. Especially Abby, where the surrogate father/daughter relationship is particularly blatant. The one possible exception, Gibbs/Jenny, is somewhat balanced out by his having been her superior in the past and her now being dead.
Among Heroes fans who shipped Mohinder and Sylar, this was a VERY popular theme in fanfic before Mohinder gave himself superpowers in Season 3. Usually, Sylar's near-godlike advantage in raw physical power was tenuously balanced by Mohinder's relative grip on sanity and his being just too pretty to kill.
The Inspector Lynley Mysteries' Fan Preferred Couple of Lynley/Havers has this in spades, in both class disparity (he's a Lord, she is very much not) and in rank (he's a Detective Inspector, she's a Detective Sergeant). This is mitigated in that by the end of the series their interactions are much more those of police partners as opposed to superior/subordinate, but there are still massive issues to overcome. The entire fandom ships them anyway.
Robin Hood had Guy/Marian (he was physically stronger, politically more powerful, and eventually stabs her to death) and Robin/Kate (he was the aristocratic lord of Locksley, she was an illiterate peasant girl). Both pairings were rife with Unfortunate Implications.
Kamen Rider OOO has quite a bit of Ho Yay for Date/Gotou: Date being around 10-15 years older, Gotou's mentor, holding the position of Kamen Rider Birth (which Gotou desperately wants to become) and physically much stronger, to the point where he can easily handle the Birth Driver whereas Gotou has to train very hard to use it.
Saeko/Kirihiko in Kamen Rider Double is a pretty tragic example, leading to Kirihiko's acceptance of his wife abusing him, and finally murdering him.
The British sitcom The Thin Blue Line has Police Inspector Fowler paired with live-in girlfriend Sergeant Dawkins.
Given Fowler's outlook on his duties however this is not a major issue. At one point he offers Dawkins some advice, half now (as her senior officer) and half when he is on break (as her boyfriend, as he is not being paid to advise people as their boyfriends and so cannot due so during work hours.)
CSI: Crime Scene Investigation was this way with Grissom and Sara and the whole boss/employee thing until it became canon.
Dom Com sitcoms often inadvertently end up creating this dynamic between the two leads, usually by making one member of the lead couple hyper-competent and always right—often to the point of being a Mary Sue—while the other is portrayed as a bumbling idiot who'd likely starve to death without the other partner helping them survive. In The Fifties, the husband would often be the Gary Stu while the wife would be the hapless, bumbling moron, but in recent decades, it's usually the other way around (see: Everybody Loves Raymond).
Both the main ships involving Harvey Specter in Suits count as this - for Harvey/Donna, she's his assistant, and for Harvey/Mike, he's his associate. Less prominent with Harvey/Donna because she pretty much runs his life, so it's kind of a "who's really the boss?" question.
Unsurprizingly, as a soap opera about class differences in early-twentieth-century Britain, Downton Abbey has more than its fair share of this.
Lady Mary originally scorns Matthew as a suitor, even though he's now the heir to her family's fabulous estate, because of his middle-class background. Her sister, Lady Sybil, on the other hand falls in love with and marries the family's chauffeur, Branson. Mary eventually falls for Matthew, and both marriages are happy ones...for a while.
Also, after Sybil dies, a maid hits on Tom. She is summarily dismissed.
Even the earl himself gets in on the action when he smooches on a maid. Plus, he's married.
Theatre
Averted in the play version of My Fair Lady with Eliza being fond of the professor, but unable to have a serious relationship with him because of the power imbalance.
Videogames
Metal Gear Solid has one or two of these - including the (fairly popular and canon) background pairing in the third game of Colonel Volgin and Major Raikov. Volgin is around seven feet tall, musclebound, sadistic and ELECTRIC, not to mention years Ivan's senior. Raikov appears to be a Bishounen with occasional violent tendencies and a penchant for scanty underwear. (And the... whole... rank thing.)
Sengoku Basara has this with any ship that doesn't involve rival daimyo, especially any lord/vassal pairing you'd care to name. Probably the biggest one is DateMasamune with his second-in-command KatakuraKojuro. Given Kojuro's insane loyalty and the retainer-lord obligations of the time, the power imbalance would be mind boggling, except Kojuro is ten years older than Masamune, personally responsible for most of the army's strategy that isn't limited to "charge into battle screaming in Engrish and do crazy shit" and has, in both anime and video game canon, kicked his lord's ass, hard, when Masamune was being suicidally stupid (although both times afterward he tried to kill himself for having raised his blade to Masamune. That didn't go over well.). Close runner-up is Sanada Yukimura/Sarutobi Sasuke; see the entry on Jeeves and Wooster (although Yukimura is less dense than Bertie and more hot-blooded).
Touhou fandom has people shipping everyone with everyone else, which leads to many cases of this. One of the most popular is Yuyuko Saigyouji/Youmu Konpaku. Yuyuko is the Queen of Hakugyokurou, absolute ruler of the Netherworld and holding mastery over death. Youmu is... well, her official title is Hakugyokurou's gardener. The fact Yuyuko looks thirty-something while you'd be hard-pressed to think of Youmu as older than sixteen also factors for this trope.
The same for the Remilia Scarlet / Sakuya Izayoi pairing, the former a centuries-old terror of the night while the latter is a human probably no older than her early twenties. This mostly revolves around the persistent mystery of why a powerful, capable individual has dedicated herself to a capricious, over-bearing, literally childish being, most common theories involving some variation of Subordinate Excuse.
Eirin Yagokoro / Kaguya Houraisan also falls into this, but not the way most expect. While Kaguya does have authority over Eirin, Eirin is actually far more powerful than Kaguya and the arrangement is entirely at Eirin's discretion (she could leave whenever she wants, she just doesn't want to).
Gears of War 2 rather strongly implies that Sergeant Marcus Fenix and Lieutenant Anya Stroud have a relationship that goes past the professional.
Nowel and her loyal servant Ruru in Magical Battle Arena. The prologue of Ruru's scenario outright states that the only wish in Ruru's heart is to be with Nowel. As a fan-translator put it, Ruru almost out-gays the Lyrical Nanohacast.
Gumshoe/Edgeworth has a small but loyal following in Ace Attorney fandom, even though Edgeworth has reduced Gumshoe's pay so much that he's forced to subsist on a diet of instant noodles.
Implied in Knights of the Old Republic if your character is male, has a relationship with Bastila and chooses to fall to The Dark Side at her prompting. She becomes both "your lover and apprentice", in her words.
In Star Wars: The Old Republic, at least one love interest each for the Jedi Consular, Jedi Knight, and Sith Warrior is the player's apprentice. For the Trooper the love interest is a lower ranked member of your squad.
Just about any pairing involving Shepard in the Mass Effect series, because of the fact that (s)he's the captain of the Normandy and all of the squad members are his/her subordinates, but especially Shepard/Ashley and Shepard/Kaidan; all three of them are in the Alliance navy and Shepard outranks both Ash and Kaidan. As Shepard points out, though, what with the Saren and the Reapers and all, being caught fraternizing is the least of their problems.
Ashley touches on this trope in an e-mail to one of her sisters, says that she would never get together with one of her subordinates because if she has to decide who lives and who dies, she doesn't want love to factor into her decision. This becomes Harsher in Hindsight when you consider that on Virmire, Shepard has to choose between her and Kaidan, both of whom can be romanced. Ashley can, depending on the player's choices, be sacrificed for a romanced Kaidan or saved because Shepard is in a romance with her..
Even the romance options who are not technically subordinates (having volunteered to help out and being outside the military chain of command,) have this to some extent; even those with strong and independent personalities who could easily be the Hero of Another Story tend to be very much in Shepard's shadow, never question Shepard's leadership for a moment, and (even if they disapprove,) inevitably go along with any decision Shepard makes.
In The Orion Conspiracy, Devlin finds out early on that Captain LaPaz and Lowe (who is on a lower rank than LaPaz) are married. This becomes a plot point later on when Devlin finds out that LaPaz is eight weeks pregnant and has to use this information to blackmail her into giving him the keys to his son Danny's cupboard.
Webcomics
In Angels2200, this is an issue for Kid and her friend and squad leader Hammer. As time goes on and the Icebreakers start heading into battle, forcing Hammer to take on the responsibilities of a leader (including reprimanding Kid for not taking a shot against an enemy and almost getting Bubblegum killed), Hammer tries to distance herself from Kid in spite of her feelings, but is told that it may not be the best way to go about it. Hammer ends up falling short of telling Kid how she feels during the mission on the Ellie Arroway, and seemingly dies, only to be captured by the colonials, unbeknownst to Kid.
Pairing any of the Trolls in Homestuck is bound to lead to this, because they're all at different levels on their Fantastic Caste System. Equius/Aradia is the only one brought up in canon, because he's very proud of his noble status and she's about as common as it's possible to be.
In Girl Genius, Violeta point out to Tarvek that he may have his chance with Agatha because Agatha/Gil is an unequal pairing which can burst into flames (which is true, but it means there is no possible equal pairing for Gil), while Agatha/Tarvek is an equal pairing.
Of course, this only works as long as Tarvek doesn't claim the Lightning Throne, and then the situation reverses. Of course being the Heterodyne it's hard to imagine Agatha as unequal to anyone.
Canonically occurs twice in Teenage Mutant Ninja Turtles (2003), first between Karai, second-in-command (and later, head) of the Foot Clan, and Dr. Chaplin, the company's head scientist; and, to a lesser extent, between Starlee Hambrath—a Teen Genius interning for O'Neil Tech — and Cody Jones, O'Neil Tech's owner.
Most pairings involving Megatron and his subordinates in Transformers involve this. A bit less so with Optimus Prime, but the power difference is still there.
Batman The Animated Series (technically, Batman Beyond) gave us Batman/Batgirl. It's long over by the time we and Terry learn of it. His reaction can be summed up as "Wait, what? Whoa."
Nightwing's was worse, as he appeared to cut off all ties with both of them.
There's also Azula/Ty-Lee, Azula/Suki, and even Aang/Katara. There's also the very canon couple of Zuko/Mai, considering Zuko is heir to the throne. (Not to suggest in any way that Mai is any way less competant than Zu-Zu... just less in the "Inheriting the throne" way).
Aang/Katara is hardly unequal by the time they get together in canon. It would be unequal if they had gotten together any earlier.
There's a really great fic that plays with the power dynamics involved in shipping Zuko and Lt. Jee. On one hand, you have Prince/Commoner. On the other, you have middle-aged man/16-year-old boy. On still another hand, you have legitimate ship captain/his superior who holds no actual rank. Both are stubborn and neither of them really likes the other. Conflict ensues.
A common pairing in Danny Phantom is Vlad/Danny. Vlad is literally old enough to be Danny's dad (Vlad and Jack went to college together). In canon, he actually wants to make Danny his son, which is kinda creepy. And then you have Vlad's general Magnificent Bastard-ness. This one is fetishized to the point that rapefic is practically the norm. Don't believe me? Here's an example.
This is frequently compared to Slade/Robin, which is like Batman/Batgirl combined with the above.
My Little Pony: Friendship Is Magic fandom has the relatively common shipping of Princess Celestia, a multi-thousand-year-old Physical Goddess who controls the rising and setting of the Sun and is the unquestioned diarch of Equestria, with Twilight Sparkle, who is (aside from magical prowess) a relatively normal unicorn filly who is her student—and somewhat socially naive, to boot. Other fanfics ship Celestia's sister Luna with Twilight Sparkle, Trixie, or Fluttershy.
Thanks to Twilight ascending to alicorn-hood, the first pairing is now somewhat more equal, but Twilight would still be the far less powerful of the pair.
Real Life
The US Armed Forces actually have regulations in place to prevent this sort of thing (particularly between enlisted personnel and officers).
At least within their own commands. Military personnel of different ranks in different commands or branches are allowed to have personal relationships.
Not quite. Officer/enlisted or even junior enlisted/NCO pairs are frowned upon, and can still be a court-martial offense.
Any relationship between a slave and their slaveowner will qualify as this.
