In Code Geass, Schneizel and the Chinese eunuchs set up an Arranged Marriage between Crown Prince Odysseus (around 30), and Empress Tianzi (13).
Supplementary materials indicate that, prior to Britannia curbstomping Japan, Genbu Kururugi was considering marrying Nunally (she was 8 at the time), thinking this would deter Britannia from invading. Neither Lelouch nor Suzaku were particularly happy with that idea (Suzaku proposed marrying her instead of his father, but since he was already engaged, that didn't work out). Lelouch talks Genbu out of it offscreen.
In the manga Adarshan no Hanayome, Prince Alexid, in his 20s, weds Princess Justinia, age 10, in a political marriage. It's less squicky than it sounds, because he's self imposing a Jail Bait Wait and it is implied that as she grows up he will genuinely fall in love with her.
Averted by Doctor Irie (late twenties/early thirties) from Higurashi no Naku Koro ni; he expresses his wish to marry Satoko (between nine and thirteen years old), but quickly follows up by saying he'd wait until she's of age.
Inverted by Otoyomegatari: Karluk is 12, his wife Amir is 20. However they are also very much in love.
The movie Osama ends with the main character, a female child, getting married off to a man old enough to be her grandfather or even her grandfather's father. The scene right before the last scene is on the wedding day, focusing on how terrified the girl is and how much the other wives hate their husband. The very last scene is at night, showing the old man happy and content, performing the holy cleansing ritual that he had earlier in the movie taught a class of young boys that every good man is supposed to do after he has screwed his wife.
Deepa Mehta's Water features an eight-year-old girl who was married so young she barely remembers it, has not seen her husband in years, and is now a widow sent to live in an ashram for the rest of her life. Some of the other characters are implied to have been married at least as young, if not widowed quite so early.
The Parent Trap uses this trope as an indirect accusation, delivered with Sugary Malice. When the father tells his daughter that Meredith is about to become part of the family, she surely understands right away that he's talking about marriage. However, she pretends to innocently misunderstand him and gets all ecstatic about how he's finally getting one more daughter by adopting her.
Marianna Ucría is forced to marry her uncle when she is 13.
In The Jewel Of Medina, the Arranged Marriage between the prophet Muhammed (who was in his fifties) and the nine years old girl Aisha is portrayed as the coolest thing ever. The story practically casts her as a young superheroine on team righteous, under the benevolent leadership of her husband. The book subscribes to the theory that they waited a few more years before starting having sex, reducing the squick although not removing it completely.
A Song of Ice and Fire, which is happy to portray just how weird medieval times were, does a bit of this. When Catelyn finds out that her sister Lysa (teens at the time) was promised to Jon Arryn (early sixties at the time) in a political marriage, she realizes that may be one of the reasons why Lysa's so fucked up. And the Lannisters have one of their younger cousins, Tyrek, married to a babynote Though there's no suggestion that the marriage was consummated or is intended to be for many years. because she's the last heir of a noble house that they wish to bring under their banners. He gains the mocking nickname "wet nurse". At the start of the series Lord Walder Frey recently married his eighth wife, on his ninetieth birthday. For the record, she's younger than some of his great grandchildren, and pregnant.
Played with in the case of Arianne Martell, who while still unmarried at the time we meet her, has been proposed as a potential bride for a number of men, all of whom are old enough to be her grandfather. She's informed her father that if he wants her to actually marry, he's going to have to find her a husband young enough to still have his own teeth. As it happens, he doesn't want her to marry just yet and is suggesting old men precisely because he knows she'll refuse them.
Teased relentlessly in Sansa Stark; she begins the books at age 11. Engaged for the first few books to a (psychopathic) boy her own age, it's pretty clear from the beginning that that won't happen. A day or two after her first period, she is forcibly married to Tyrion Lannister (mid-twenties), who refuses to consummate it because she is unwilling and too young. His father demands that he rape the girl to make the marriage legitimate. She's rescued by Littlefinger (mid-thirties), who spends the next couple books making creepy advances at her; it turns out later that he'd tried to get approval to forcibly marry her as well. Meanwhile, she's been unofficially engaged to her own cousin, a boy of five. Thus putting her on both sides of the trope at the same time.
Gender-flipped in the Trickster duet, where regents attempt a political match between the six-year-old king and a fifteen-year-old girl, and later her twelve-year-old sister when the elder elopes with a noble from a neighboring country. The marriage never happens, though.
The Last Days of the Jannissaries, Villain Protagonist Pasha Ali Tepelini is married to a young girl, whom he loves very much. Incidentally, she loves him too, until she discovers that he's being a complete jerkass, and betrays him. She's willing to forgive her husband towards the end though, and is genuinely worried for his safety, when the sultan's assassin shows up to take his head.
In the Honor Harrington novella "Promised Land" (in The Service of the Sword), Ephraim Templeton (55) adds kidnap victim Judith (12) to his collection of wives. That's the least vile thing he does. It comes back to bite him hard by the end.
Subverted in The Chronicles Of Narnia. Aravis Tarkheena is betrothed to an older man...but she escapes on time, and eventually marries someone her age that she truly loves.
Her best friend Lasaraleen, however, goes through with her Arranged Marriage and doesn't seem to understand why Aravis wouldn't want to. However, she's sort of a Lovable Libby more concerned with her husband's money and position.
In Crime And Punishment, Svidrigrailov, a man in his 60s, gets engaged to a 14-year-old girl. Although it wasn't too unusual for people to get married that young back then, such a huge age difference definitely was, and the whole thing is very much played as Squicky. Even Svidrigrailov himself seems to realise it, as afterwards he has a dream in which a five-year-old girl attempts to seduce him, which thoroughly creeps him out, and soon after he commits suicide.
The Wife of Bath was first married to an old man when she was twelve years old.
15-year-old Kaede from Tales Of The Otori is first engaged to a man who dies of old age before they are even officially married.
Law & Order: SVU had a case along these lines. The marriage was not legally binding, but it was treated as a real marriage by the cultists.
It also produced a pregnancy, which is what kickstarted the whole episode, when the child was checked into a hospital.
Not "old" per se, but in season one of Blackadder, Prince Edmund marries the 8-year old Princess Leia of Hungary, much to his own dismay. Subverted somewhat as the marriage is purely political and completely platonic, with Leia even serving as something of a Morality Pet for Edmund. They spend their wedding night with Edmund reading her a bedtime story.
In the Police Squad! episode "Testimony of Evil" (a.k.a. "Dead Men Don't Laugh"), Ed Hocken describes a man as "Married, one child. That didn't work out so he married a grown woman."
Series 1 of Big Love introduces us to Rhonda, the 16 year-old girl promised to fundamentalist Mormon prophet Roman Grant; the marriage doesn't go ahead, but such marriages are presented as common on the Juniper Creek compound. Later in series 3, Nicki manages to prevent her 14 year-old daughter Cara Lynn from being married off to a much older man.
In "I, Claudius", the empress is apalled that young men are not bothering to get married and orders that there better be some marriages soon. She then warns them that there better not be any engagements to children just so they can put of marrying them for a decade.
In the Criminal Minds episode "Minimal Loss", cult leader Benjamin Cyrus (played by Luke Perry) marries a 15-year-old girl, and has his way with whatever woman he wants in the cult, as per his own decree.
Blutengels song "Black Wedding" can be interpreted this way.
Rod Stewart's "Tonight's The Night (Gonna Be Alright)" has also been interpreted as an older man coming on to a teen-aged girl ... and wanting to consumate something more than just a sexual relationship.
Mitsuru's Social Link in Persona 3 involves the board of directors arranging for her to marry a much older man (She's about to graduate from high school, he's at least in his thirties) to stabilize the Kirijo Group after her father's death.
In Suikoden the vampire Neclord makes a habit of abducting young women to make them his bride. After building his castle near the Warriors Village he visits said location and demands a new bride every year.
In one Chick Tract called "The Little Bride", the marriage between Aisha and Muhammed is used to condemn Islam, highlighting that she was only 6 when they got engaged and only 9 when they got married. The tract draws the conclusion that Muhammed was a pedophile rapist.
Thankfully averted in The Smurfs episode "Romeo And Smurfette" when Papa Smurf along with the other Smurfs start having those thoughts about marrying Smurfette, but she even turns her peers down by stating that she's still too young and that she loves all her fellow Smurfs equally.