There is a valuable thing out there. It's one-of-a-kind, which makes it the greatest prize ever. That means someone wants it, just for that reason, by any means.
Note it's not the artifact hypnotically seducing the person into wanting it. The person is just that selfish or greedy. Nor is it something earned; it's outright taken. It also doesn't count if someone steals it for the thrill of the theft, or to just show how good a thief he/she is. Either the thief has to want it, or he/she is stealing it for someone who does.
Note that this rarely ends well, no matter whether the story is idealistic or cynical. That person stole something they shouldn't keep. In idealistic stories, it's too important to lock away. In cynical stories, it's too dangerous to try to lock away.
- That Gelarden or Lawrence III, depending on the language, in Pokémon 2000 who captured the Legendary Birds.
- Lupin III doesn't count for this trope. He never wants it for the rarity, and has often taken something just to make sure someone else doesn't have it. On the other hand, Fujiko is also the cause of many of their capers. To the point where Jigen will try to quit the job once he hears it was her idea.
- The actions of Fiamma of the Right, the former Man Behind the Man of the Roman Catholic and Russian Orthodox Churches in A Certain Magical Index, are guided solely by his obsession with possessing Touma's Imagine Breaker and becoming more powerful than God himself.
- Professir Machinegal in Moldiver has this as his main motivation for being a supervillain. He already is wealthy, respected and famous, but there are technological artifacts he can only get by stealing, and he doesn't think anyone but him are worthy of them anyway.
- In Shakugan no Shana, the villain Sorath was obsessed with obtaining Shana's Flaming Sword Nietono no Shana. When he manages to steal it, he throws away his own Cool Sword Blutsauger.
- There's also a Marvel Comics character named The Collector, who collected unique specimens from across the universe.
- The original motivation of the Batman villain the Cavalier was to obtain unique pieces that he was unable to purchase for his collection.
- Green Lantern: Larfleeze wants everything, but especially rare things, like Lantern rings he's never seen before.
- Superboy 1994: Scavenger wants all the extraterrestrial tech and magical items around Hawaii. When a spear with rumored magical properties is featured on the news he says is must be his before teleporting in and stealing it after Superboy has already been knocked for a loop by Knockout.
- Most of the characters in The Maltese Falcon will go to any lengths to obtain the fabled bird.
- Ublaz Mad Eyes in The Pearls of Lutra from the Redwall series is obsessed with the titular pearls, known as "the Tears of All Oceans". He has a crown already made with six empty facets in which to place the pearls, and wants them badly enough to send multiple expeditions out to Mossflower to find them, resulting in the slaughter of an entire hold of otters (save one) and the abduction of innocent Abbeydwellers just to satisfy his vanity.
- There is a story where a princess (or maybe duchess) hears someone in her land has a talking cat. She wants it for herself, so she throws the owner in her dungeon. One scene has her riding in her carriage, carrying the cat in her hand muff, and the cat escapes by biting her hand.
- All of the unicorns, in The Last Unicorn, collected by King Haggard.
Haggard: They are MINE! They belong to ME! The Red Bull gathered them one-by-one and I bade him drive each one into the sea! I like to watch them. They fill me with joy. The first time I felt it, I thought I was going to die. I said to the Red Bull, 'I must have them! I must have all of them, all there are! For nothing makes me happy but their shining, and their grace.' So, the Red Bull caught them. Each time I see the unicorns — MY unicorns — it is like that morning in the woods, and I feel young, in spite of myself!
- In Robert Asprin's fantasy novel Myth Directions, Tanda the Trollop assassin ropes protagonist Skeeve into her attempt to find a truly one-of-a-kind item to give to Aahz (a scaly green Pervect) as a birthday present. She ultimately settles on a ghastly frog-scuplture trophy that has no value except as the prize for a heated sports competition between rival cities. Their robbery attempt goes horribly wrong, and things only spiral further out of control from there.
- To add to it, Skeeve tries to keep Aahz from finding out about any of this because he knows the lecture he'll get for having done something like this. When Aahz does find out and asks incredulously "This ugly statue is what's behind all this?", a frustrated Skeeve responds "Yeah, because we wanted to give it to you. Happy birthday." After a stunned minute, Aahz decides It Must Be Mine! and the group alters their escape plan to include the theft of the trophy.
- In the first Acorna book, Hafiz Harakamian sought to add Acorna to his collection of rarities as the crown jewel, a desire which quickly disappeared once he learned she wasn't some sort of mutant, but a lost member of a space-faring race.
- Simon R. Green's Nightside books feature the Collector, who is reclusive, petulant and somewhat childish in his single-minded devotion to things that — in his opinion — only he can truly appreciate.
- The Star Trek: The Next Generation episode "The Most Toys". The thing that was stolen was Lieutenant Commander Data. It probably wasn't one of Kivas Fajo's better business plans...
- An episode of Jonathan Creek had a woman and her daughter steal a valuable statue to spite its owner (the mother's brother). When the daughter went to recover it she was murdered by an Ax-Crazy, sociopathic pimp who decided he wanted it simply because he heard it was valuable.
- In Lois & Clark, a baddie captures Superman, and uses Lois Lane as hostage to make sure he doesn't escape. Which he does, via New Powers as the Plot Demands.
- The Avengers episode "The Man from Auntie" features a villainous firm which collects items like this for... collectors. The "item" they've currently stolen and plan to auction off is Emma Peel.
- Doctor Who:
- In "The Seeds of Doom", two alien pods are found in the Antarctic permafrost. The psychotic millionaire Harrison Chase sends a team of thugs to get them, because they're unique. The pods cause vegetation to kill animal life, endangering the world.
- In "City of Death", a key plot-point involves the theft of the Mona Lisa to be sold (along with six identical paintings) to finance Count Scarlioni's temporal experiments. Inspector Duggan observed to the Doctor at one point, "There are at least seven people in my address book who'd pay millions for that picture, for their own private collections. It would be an expensive gloat, but they'd do it."
- At least one Mission: Impossible episode had a millionaire who had a national treasure that the original nation wanted back, and it was important they get it for reasons of international politics. The current owner was not cooperative.
- Comes up in Dad's Army of all places where Mainwaring is trying to buy some oranges at a charity auction from the warden, who predictably is doing everything in his power to stop him getting them. Eventually Wilson tells Pike to buy an orange for Mainwaring, but neglects to tell the captain, resulting in Mainwaring entering a furious bidding war against himself. He eventually ends up paying ten shillings for it (when the first one sold for a couple of pence).
- Kamen Rider Decade: Kamen Rider Diend has a 'treasure' in each episode that he is seeking. He alone knows what makes something a 'treasure,' and he only wants it because it is one, and rarely for what it actually does (some of 'em are important to the plot.)
- Kamen Rider Kabuto: Invoked in the World of Kabuto arc, where Decade claims to have a bottle of legendary spice discovered by Vasco de Gama, which of course Diend wants. In reality it's nothing but ordinary pepper, and Decade is Trolling Diend as payback for all the trolling he usually does.
- Happens often with the marks in Hustle. Examples include a rare banknote in "The Lesson" (or so it seems), a case of rare wine in "Getting Even", and a Faberge Egg (one of a matched pair) in "Eat Yourself Slender".
- Joey Ryan's explanation for showing up in Championship Wrestling From Hollywood with the organization's television title belt, even though he never won it. As the biggest television star on the card, why shouldn't he have the belt?
- Oliver, the Duke of Tanas from Fire Emblem 9 and 10, toward the royal heron laguz.
- Chandra in Eternal Darkness says this about one of the artifacts of the Ancients, before she knew what exactly it was.
- In Mystery Of Mortlake Mansion, "R's" notes reveal that he was obsessed with the magic of Cagliostro. Too late does he realise that Evil Is Not a Toy.
- Dork Tower: This is actually Igor's Catch-Phrase, though it seems like it doesn't so much have to be a unique thing as just press his nerd buttons.
- In Nodwick's Lord of the Rings parody, the Gollum character is based on Igor above. Nodwick quickly realised that "This One Ring" is not an Artifact of Attraction as everyone believed; Smeagor was just crazy.
- There was a ThunderCats episode where some queen tried to cage a magical songbird (although its song didn't come across as beautiful as we were told).
- Superman: The Animated Series, episode "The Main Man": An alien called the Preserver has a private zoo in which every creature is the last of its kind; in the episode, it attempts to add Superman, the last Kryptonian, to its collection by hiring Lobo to capture him.
- In a Treehouse of Horror episode, Comic Book Guy is the supervillain "The Collector" who collects Lucy Lawless, the Fourth Doctor, Matt Groening, etc. He also owns the only working phaser ever made (only fired once, to keep William Shatner from making another album) and a working double-lightsaber.
Lawless: You removed it from its original packaging!Collector: No! It's no longer a collectible!
- Mr. Krabs had just sold a cap to SpongeBob SquarePants when another person showed up saying it was a rare cap and offering way more than what Spongebob paid. Krabs spent most of the episode trying to recover it and, by the time he did get it back, several others appeared, making it not so valuable anymore.
- Galaxy Goof-Ups: In "Space Station USA", once the titular station is found, the richest man in galaxy wants to add it to his space station collection and has no moral objections against stealing it.