In Junji Ito's Tomie series, the titluar character does, indeed, go after the money like a typical Black Widow... Except she gives men an odd feeling of wanting to kill her.
Roxanne in Claymore was a low ranked warrior, who consistently would become the best friend of a higher ranked warrior, learn her techniques through yoki synchronization, and kill her. This continued until she became one of the strongest and most notorious Claymores in history.
Ava Lord from Sin City turns out to be one, though she's not above having other people do her dirty work (such as Dwight McCarthy, who she tricks into murdering her innocent husband so that she can get her hands on all his money).
One of the women at the Serial Killer Convention complains about female serial killers being stereotyped as nothing but Black Widows & Killer Nurses in The Sandman book The Doll's House.
This is made all the more amusing because she says this while participating in a panel discussion on "Women In Serial Killing"... whose fellow panelists are a Black Widow and a Killer Nurse who are visibly annoyed with her. And for extra laughs she's complaining about stereotypes despite being an Asian working under the nom de guerre of "Dog Soup".
In a Nightwing Annual, Dick suspects a young woman who's buried three husbands in three years of being one of these, and decides to investigate by pretending to marry her. It's actually her former best friend, as it turns out.
"By the kindness of your heart have you been deceived, O king," said he. "Your son has married a girl who has lost a hand. Do you know why she had lost it? She was a witch, and has wedded three husbands, and each husband she has put to death with her arts. Then the people of the town cut off her hand, and turned her into the forest. And what I say is true, for her town is my town also."
Many Harry Potter fanfics embrace what in canon is only implied about Blaise Zabini's mother (as mentioned in the Literature section below). Here for example:
Blaise: *says something about his mother*
Draco: And how is husband number nine?
Blaise: Still breathing.
Pansy: For now.
When In Doubt Obliviate exaggerates this to the degree that Blaise can't keep track of the names of his stepfathers - or doesn't, intentionally, in order to be less affected by their deaths.
Gravity Falls Rule 63 has widowed mother Bonnie Gleeful, who claimed her husband died on the day her daughter, Jennifer, was born. However...
(talks to a photo of her dead husband while playfully holding a blood-stained knife) "All I needed was for you to help me conceive a child. That precious car lot of yours was a nice little bonus. Nothing personal, dear. It was all part of the plan."
Black Widow (1987), played by Theresa Russell, a serial killer of rich men she married for their money. She continues to do this long after she'd be wealthy though, implying her reasons are psychological rather than monetary.
Stepmonster. There was also a screwed up bit of Gift of the Magi in there, as the monster is a comic book creature and only a specific, very rare and very valuable issue explained how the monster can be defeated. So the kid pawns the violin his dad gave him to buy the comic book; unfortunately, his dad has something serious against comic books and rips it up, not realizing its significance (or value), and it's not until the kid finds the one missing piece - that's right, one panel out of the entire comic book divulged the monster's weakness - that the kid realizes how screwed he is. The dad redeems himself at the movie's climax in a Big Damn Heroes moment where it turns out he bought back the violin and proceeds to dispatch the monster.
Debbie Jellinsky from Addams Family Values is one of these. She gets her claws into Fester and marries him, but, Fester being one of the Addams clan, she doesn't quite succeed at the killing part.
She's been killing since childhood, and often gets rid of people who fail to meet her needs (usually money-related), starting with her parents, who she killed for not giving her a Ballerina Barbie for her birthday.
This being The Addams Family, once everyone understands the depths of her issues they all start to really empathize with her and regret not really getting to know her.
This is Mrs. White's backstory in Clue. She's had five husbands, and we learn the fate of two. One was an illusionist who disappeared and never reappeared ("He wasn't a very good illusionist"). As for the other, according to Mrs. White, someone "had cut off his head and his, well, you know."
Men should be like Kleenex, soft, strong, and disposable.
Mike Myers parodies the trope in So I Married an Axe Murderer — his character believes he is dating the mysterious "Mrs. X." She's not. Turns out her sister was an insane Clingy Jealous Girl who murdered all of the poor girl's previous husbands (she thought they had all just up and left her).
In the Laurel And Hardy short film The Private Life of Oliver the Eighth Ollie courts a wealthy widow - only to discover on the wedding night that she has murdered her seven previous husbands who were all named Oliver. Hilarity Ensues. Partly a subversion, since it is Ollie who was hoping to benefit financially from the marriage.
In Onibaba, Kichi's mother makes her living by preying on passing soldiers.
Blaise Zabini's mother is implied to be this in Harry Potter.
A real-life example is in the non-fiction book 'Homicide: A Year on the Killing Streets' (later made into the popular TV drama Homicide: Life on the Street) which goes into detail on the case of Geraldine Parish, who was murdering her husbands and relatives (using a contract killer) for insurance money. An FBI profile mentions that the typical "black widow" killer is an older and less attractive woman than the beautiful young fatales of Hollywood stereotype.
Nora Roberts, the main character in James Patterson's Honeymoon, is one of these. She kills two rich guys a short while after they propose to her with her two piece signature dish: an omelet laced with one poison, and sparkle water mixed with a second poison.
Madame Olympia and (a rare gender-flipped example) Sir Simon Montpelier in Eva Ibbotson's Which Witch?.
Simkin: I decided a change was in order, as the Duchess D'Longeville said when she married her fourth husband. Or was it her fifth? Not that it matters. He'll be dead like the others before long. Never take tea with the Duchess D'Longeville. Or, if you do, make certain she doesn't serve you from the same pot she serves her husband.
Alison, the wicked stepmother character from Mercedes Lackey's Cinderella retelling, Phoenix and Ashes. Eleanor's father and the father of the stepsisters were merely the bookends of a long career of using and killing men.
Julia Valerian is widowed twice in A Voice in the Wind, having poisoned her violent second husband; her significantly older first husband technically died of a heart attack/fall from his horse, but it’s implied that Julia’s resentment towards him, rebelliousness, and flirtations with other men contributed to his weak health.
Joanna in Ben Bova's Grand Tour series loses no less than three husbands in such a way.
Faye Cochrane in Wings was thought to be one of these in one episode, what with the mysterious deaths of all her husbands George. Although that may have been a coincidence, considering all the angst over the likely fate of her latest fiancée George during the show.
The Practice had an episode where they defended a woman accused of being a black widow, due to her habit of marrying much older men. Her most recent husband had died of a heart-attack induced by viagra.
Miss Klotz: Didn't bother me when my four ex-husbands said it; Doesn't bother me when you say it.
Carey Martin: You've been divorced four times?
Miss Klotz: Oh, no, no...widowed.
Get Smart's Maxwell Smart had to marry a KAOS agent who used this as her modus operandi for knocking off CONTROL agents in the episode "Widow Often Annie." 99 was not amused, as Max had already married her.
Stargate SG-1: It is not an actual example of the trope, she actually has a pretty effective Cartwright Curse instead (And provides a page quote), but Samantha Carter's boyfriends all seem to wind up six feet under in pretty short order (Unless you're MacGyver). DVD audio commentary reveals that the writers actually called her "Black Widow Carter," and were going to title an episode as such until they went with Chimera.
Minus the wealth part, on CSI: Crime Scene Investigation the youngest daughter of a compulsive hoarder seduced boys from the halfway house where her brother worked and after she killed them to make sure they wouldn't leave she hid them around her mother's cluttered house. When mom found out what was happening she handcuffed her daughter to her bed and barricaded her behind a wall of boxes, and when her other daughter found one of the bodies she got hit on the head and left to die in a pile of newspapers.
They also did an episode where two women conspired to act as wife and secretary for their victim and poisoned him with Selenium (and further investigation revealed they had done the same previously). Unusually, our heroes weren't able to prove either of them guilty.
Slightly subverted in that the wife actually fell in love with her husband, despite his numerous infidelities, and was considering backing out of the deal.
Mystery Science Theater 3000: The It Lives by Night episode ends with Pearl Forrester regaling Professor Bobo and Brain Guy with slides from her numerous honeymoons, and descriptions of the untimely demises that each of her husbands and fiancés met with.
White Collar: In "Veiled Threat", Neal, Peter and and Jones go undercover as wealthy bachelors to snare a black widow. She latches onto Peter, much to his consternation (what with his adorable attachment to Elizabeth).
Batman once had to capture a criminal known as the Black Widow. Her deceased husband's name was Max Black. However, instead of having to prevent her from killing husbands for money, he had to prevent her from robbing banks.
In a two-parter featuring a villain known as the Sandman (not that one) who plans to marry and rob a rich insomniac widow (he's posing as a sleep doctor). However, when she starts prattling on about the fates of her previous four husbands the viewer is left to wonder if she's a Black Widow or just ridiculously unlucky.
The 1975 Alice Cooper song "The Black Widow" depicts this with a opening spoken-word part (by Vincent Price) carefully describing the female black widow spider's lethality and mating habits. Unfortunately, the song itself negates this lesson both by making the spider character male and by depicting him as a Depraved Bisexual.
The song "To Keep My Love Alive" is all about this trope.
Though it's not spelled out in so many words, "I'm Henry VIII, I Am" by Herman's Hermits could be interpreted as being about this from the perspective of the latest victim. Which would also make the song a classic of Lyrical Dissonance. (It's also amusing considering the real life Henry VIII is considered this trope's Distaff Counterpart, The Bluebeard.)
Religion and Mythology
Subverted in the Book of Tobit: a woman named Sarah has lost seven husbands before any of her marriages could be consummated, but it's because a demon named Asmodeus is in lust with her and doesn't like the competition. The Archangel Raphael fixes this problem by advising her cousin, Tobias, to marry her, and teaching him how to drive Asmodeus away.
Natasha Kerensky from BattleTech. She became known by her moniker after her lover (who was one of the founders of the renowned Wolf's Dragoons) was taken hostage and later killed by Anton Marik, due to a fallout in relations. She reacted violently to this and lead her unit to storm Marik's stronghold and kill him and his remaining forces.
Ravenloft uses this trope with Ivana Boritsi (who's even called "the Black Widow") and her mother Camille. Also done with the red widow monster, which seduce men in their guise as gorgeous redheads, then paralyze them and fill their bodies with eggs.
The Dark Eye has Alara Paligan, widow of Emperor Hal and grandmother of the current Empress. Though she's not actually a self-made widow, she is a grand weaver of intrigue, and her soul animal is a black widow spider.
The latest Revamp of The Haunted Mansion at Disney Theme Parks replaced the bride in the attic with a creepy Axe-wielding Black Widow Bride - cackling wedding vows including "In sickness and in... Wealth" (being proceeded by portraits of her former husbands' heads disappearing after a chopping noise).
The band My X was the main attraction at Busch Gardens' Howl-O-Scream 2010. It used to be called XY, but female lead Sylvie took over the band and renamed it when the male lead/her ( apparently abusive) boyfriend mysteriously vanished. Now Sylvie spends her nights picking out guys from the concert crowd, hooking up with them backstage, and bringing them to her dressing room where she hangs them up, chops off their fingers, and kills them. Check out their signature song. (My X was actually an unsigned band from Tampa; they renamed the band and wrote three new songs for the park's Halloween special.)
There's a player challenge for The Sims 2 that revolves around creating one of these.See it here.
Also in the pre-made neighborhood Strangetown, Olive Specter is implied to be one of these. And for the bonus Visual Pun, she is indeed black.
Ghostbusters: The Video Game. In the second visit to the Hotel Sedgewick you fight the "Spider Witch", the ghost of a woman who murdered her previous husbands who takes the form of a giant spider. She hung them upside down and drained them of all their blood in the service of Gozer's cult. It's not clear if she did this before or after she killed them.
Although her partners tend to still be alive. Until the vault hunters see to that. Her first husband forced her to kill him after threatening to enslave their daughter as the "clan wife", her second husband was a serial killer taken down by the players (and emotionally mourned by Moxxi), her third husband is the amoral gun runner supplying to the players, and various lovers were murdered either by the players or Moxxi's son. Less a black widow, more a dubious judge of character.
Mass Effect 2 reveals that a small percentage of Asari suffer from a genetic defect that causes their Mind Meld-esque mating to kill their partners. Ardat-Yakshi("Demon of the Night Winds") who kill in this manner experience an addictive rush when this occurs, as well as an increase in biotic ability. They are a variant of this trope because most Ardat-Yakshi hunt for victims to satiate their addiction rather than for money.
Morinth is the first example, and a highly successful one, having done this for 400 years. She seeks out interesting individuals, generally strong, clever, or artistic, and seduces them. She rarely stays in one location for long, both due to the number of bodies she leaves behind and the Justiciar dedicated to killing her.
Lady D from Henry Hatsworth, who hangs around a graveyard swamp and stands on a giant wedding cake/fort, shooting skulls out of a fake groom at anyone who rejects her.
In A Vampyre Story, the Baroness, previous owner of the castle in which the protagonist is currently imprisoned, is heavily implied to be one of these; that, or crazy unlucky in marriage. In her old bedroom is a shelf full of funerary urns, each containing the remains of a husband. Whatever the reason, she's spent so little time actually married that she has to resort to black magic in order to have a child, namely the villain of the piece (well, maybe "resort" is the wrong word; she was a witch to begin with).
In Fallout 3, your female character can learn an ability by this name, which allows you to charm and manipulate members of the opposite sex with ease. Also, this perk grants a minor combat damage increase against male characters. Lady Killer is essentially the same perk for men.
Also the moniker of Penelope Chase, former leader of the Slavers.
In World of Warcraft, it's implied that Elder Crone Magatha Grimtotem murdered her husband, the chief of the Grimtotem clan of tauren, to claim his leadership position.
The Contessa of Sly Cooper 2 is implied to be this. While it is never explicitly stated that she killed her wealthy husband, she definitely used his money for illegal purposes after his death.
Lucrezia Flathead of Zork Zero was married eighteen times, and none of the husbands lasted more than ten months. Fourteen of them died on the wedding night. Some of the details provided in her biography make it pretty obvious that the deaths were not accidental, though nobody at the time (Including the biographer) was able to figure this out.
Blackarachnia (who is an actual black widow spider, or at least turns into one) threatens to do this to Silverbolt in Beast Wars, citing her beast mode's predilection towards eating their mates. The fact that he still refuses to stop loving her both endears Silverbolt to her and makes her think he's a moron.
Subverted on American Dad—ever since Stan's dad walked out on her, his mother's new beaus always disappear after their third date. Francine and Roger believe that she's killing them, when actually Stan is kidnapping them to make sure she never has her heart broken again.
In Code Monkeys, Mr. Larrity is a rare, repeatedly successful male example. How he can keep this success when he profits obscenely off of it and stuffs his wives to keep in his office, we don't know.
Mary Ann Cotton ("she's dead and she's rotten"), who killed three husbands and at least eleven of her children in Victorian County Durham, to a large extent for the insurance money.
Even worse was that she used the same method for all of them: arsenic. And yet nobody noticed until she happened to slip up and mention that her last (then apparently healthy) little boy would "probably go like the rest of them" while speaking to a local preacher.
Black Widow Spiders, Praying Mantis, and too many insects to count. Though interestingly, the spiders that give this trope its name have a number of different species, and most do not kill their mates and let them hang around in their webs for a while. Also, usually the male spiders offer themselves because they could only mate once anyway and if the female gets to eat, they usually have a higher chance of having offspring.
"Black Widow" is the official FBI designation for this type of killer.
The whole point of the Oxygen channel's show Snapped. The show highlights women who killed their husbands (usually for the insurance money). At least, when the show isn't making the victim out to be an asshole.
Annie Palmer, the (in)famous "White Witch of Rose Hall", who resided at the eponymous plantation outside of Montego Bay, St. James in Jamaica, and who is reported to have murdered three husbands and countless lovers, as well as many of her slaves.
Margaret Rudin, who married five times and at least two of her husbands perished in very strange circumstances. The fifth one, Ron Rudin, turned out to be somewhat more Genre Savvythan believed...