Break the Fake

A character has recently bought an interesting or rare item from a shady seller, or perhaps has stolen a prized treasure from somewhere. Oh no! It's a fake! And you know what the first thing you do to a fake is, right? Smash it! Break it! Basically destroy it somehow. Used often with gems that turn out to be glass, because they make great smashy sounds or can be ground up in a powerful fist.

This is usually done to prove to a doubter that it is a fake, but can also be done by accident to reveal that it's fake, or simply done in anger after you find out it is. The most common aversion of this is with fake paintings, which never seem to be destroyed after they're revealed to be counterfeit, and are either kept by the owner anyway ("oh well, it still looks nice") or kept by the police as evidence, if the owner doesn't try to sell it on to the next naive idiot.

Anime and Manga

 * Averted in Gunslinger Girl when the fake antique kaleidoscope is damaged, but repaired, despite the fact that everyone involved suspects it's a fake.
 * Played with in Hunter X Hunter. An episode is dedicated to someone who makes counterfeits of rare artifacts. They come across an artifact at an auction: A sealed clay container for valuable jewels. The only surefire way to determine its authenticity is to break it and see the contents inside, but this would ruin its value as an artifact. The counterfeiter gets into a heated debate with an appraiser over its authenticity, both trying their hard not to resort to breaking the object. The counterfeiter ultimately convinces the appraiser that it's fake,
 * Inverted in Dragonball: A peddler sells the villains what looks like a genuine dragonball, until it is accidentally dropped and shatters. Colonel Silver apparently deduced it was fake all along, however.
 * Yu-Gi-Oh: Odion's fake Millennium Rod shatters when he's struck by lightning, confirming it was a fake and that he's not the Big Bad like they assumed.
 * Bleach anime episode 137. After the arrancar Patros is defeated, the Hogyoku he stole from Lord Aizen breaks into pieces. Kisuke Urahara explains that Aizen let Patros steal a fake Hogyoku, because the real Hogyoku would never have broken so easily.

Film

 * In Octopussy, General Orlav smashes a real (in-universe) Fabergé egg, having been inadvertently tricked by James Bond, who switched a real and a fake much earlier in the film. The jewelsmith flinches at the sight, but since Bond had planted a bug in the real one, it's not an entirely unproductive move on Orlov's part.
 * Invoked in Dreamworks' Flushed Away when Roddy smashes Rita's prized ruby to prove that it's fake.
 * In Captain America the First Avenger, Schmidt breaks the fake Tesseract.
 * Done in the Russian comedy Shirly-Myrly by a man who wants to buy a huge diamond. The one really shocked, BTW, is the seller, who never let another man hold the suitca- Oh Crap!

Literature

 * In M.Y.T.H. Inc. Link, Skeeve has his dragon Gleep burn the consignment of comic books when he realizes they're fake. Justified because he doesn't want to let them be sold to gullible buyers, and is willing to catch flak for failing to protect the shipment.
 * One of the characters in The Joy Luck Club was the daughter of a woman who had been forced into concubinage. The wife gave the daughter a lovely string of 'pearls,' but the mother crushed one to show her that they were only glass.
 * Done in the first book of The Sword of Truth series by Darken Rahl's bodyguard.

Live Action Television

 * In Young Blades, Siroc examines what he believes to be a fake diamond. He smashes it into powder, proving that it is fake, because a real diamond wouldn't be so easy to destroy. (Much to the chagrin of the other Musketeers, who helped pay for what was sold as a real diamond, and planned to return it to the pawn shop after Siroc was done studying it.)
 * On the CSI episode "Suckers", Nick accidentally damages a samurai sword from a collection of Japanese artifacts, but discovers that it's a forgery because of what the damage reveals. The whole team then disassembles the entire collection, as it's all fake and taking it apart may provide evidence to explain the scam.
 * Nate does this on Leverage in "The Rashomon Job". A bejeweled dagger is being displayed in a museum, and at the end of a series of crazy events, Nate ends up with the dagger, confronts the curator with it... and breaks it, knowing it's really a fake (the real one ).
 * The short Sci-Fi series The Lost Room featured a number of strange Objects with seemingly random supernatural powers, all connected to a physics-breaking disaster at a motel in the middle of nowhere that resulted in a room and its contents being shifted out of our universe (hence the title). The only thing the Objects had in common was that they were all indestructible, and therefore attempting to break, burn or tear something suspected of being an Object was a common way of identifying fakes.

Real Life

 * PayPal requires unwitting purchasers of counterfeit (or allegedly counterfeit) items to destroy the item and send them a picture.
 * Numerous online examples, usually as a way of venting frustration with being ripped off.
 * Customs officers worldwide commonly do this with stashes of counterfeit goods they detect entering into their country.
 * Norbert Casteret wrore in his autobiographic book how he and a friend slipped another friend an "archeological finding" as a prank. After they told him it's a fake, he refused to believe and dared them to break it...

Western Animation

 * In an episode of Gargoyles, Kings Arthur and MacBeth are fighting over Excalibur. Macbeth claims the sword from the dragon statue, but then eventually loses his grip on it. Arthur picks it up, and then smashes it, revealing it's a fake. He'd know how the genuine article felt in his hands.
 * Subverted in The Proud Family. When one of Penny's relatives comes to visit, she gives Suga Mama some diamonds. Suga Mama initially thinks they are fake and tests it on a window. The window cracks upon her scratching the window with it, causing her to realize that they actually are diamonds.