Battle Trophy

One way to celebrate a victory, as well as to remember a foe that is particularly hated or respected, is to take a piece of them as a keepsake.

The object in question should be something personal and connected with the enemy, such as an Iconic Item or, more morbidly, part of their own body. The victor might wear this piece, either to impress his allies or to taunt or demoralise his remaining enemies.

On a larger scale, one country can do this to another, taking a captured land's artworks and sigils for its own.

These might be kept in a Trophy Room or, especially for heads, mounted on a wall. In Video Games, this is often combined with And Your Reward Is Interior Decorating.

Related to Creepy Souvenir. Superhero Trophy Shelf is a subtrope.

Examples of Battle Trophy include:

Anime and Manga

In Ghost in The Shell Stand Alone Complex's second season, Kuze keeps Batou's knife after beating him in a fight. He reclaims it in the final episode, when Kuze surrenders.

Comic Books

Almost every incarnation of Batman collects items he gained from his enemies like weapons and costumes. In fact the giant penny was from a case where the Penny Plunder tried to steal it. It was later changed to Two-Face trying to steal it.

Film

Undercover Brother. When the title character was a child his father gave him a medallion so he would never forget who he was or what he stood for. When Mr. Feather captures Undercover Brother he rips the medallion off his neck and says "So I can always have something to remember you by."
Superman II. Ursa rips off a piece of the clothing of people she defeats. She ripped the patch off the suit of an astronaut on the Moon, killing him through explosive decompression, and the badge of a deputy sheriff on Earth. By the end of the film she had a collection of them on her uniform.
In the movie Sky High, The Commander and Jetstream has an entire section of their base to show off stuff taken from defeated opponents.
In Star Wars, General Grievous' lightsabers come from slain Jedi.
In the 2007 TMNT movie, Splinter keeps a trophy shelf that includes Shredder's Helmet from Teenage Mutant Ninja Turtles, the ooze canister from Secret Of The Ooze and the Time Scepter from Ninja Turtles 3 among other Continuity Nods. They then add Winter's Helmet, Nightwatcher's Helmet and Cowabunga Carl's mask to the shelf too.

Literature

Although she didn't kill him herself, Delores Umbridge's appropriation of Mad-Eye Moody's eye in Harry Potter has this kind of intent.
The Black Ears from A Song of Ice and Fire books are a tribe of hillmen that rip off the ears of captured prisioners and keep them as trophies.
In The Things They Carried, some soldiers cut off thumbs and things from dead VC. This is to a certain extent Truth in Television.

Live Action TV

In Buffy the Vampire Slayer, Spike's duster is revealed to be this in the episode "Fool For Love." He took it from the second slayer he defeated.
The Doctor of Doctor Who keeps a snow globe containing the Carrionites in a suitcase next to his Agatha Christie books.
Dexter from Dexter takes a blood sample from every killer he's killed.

Religion

According to The Bible, the Philistines captured the Ark of the Covenant and paraded around with it for a while. This turned out to be a bad idea, and they eventually gave it back.

Tabletop RPG

In Nomine supplement Superiors 1: War and Honor. Angels who follow the Archangel Michael have been known to take the weapons, insignia or even body parts of defeated demons as trophies. A few of them have necklaces of demon ears.
Pretty much everybody in Warhammer 40000.
Dungeons and Dragons
- 3rd Edition
  - The Chull takes trophies from its victims, such as weapons, armor and other belongings. If the victim has nothing, the Chull removes and keeps its skull.
  - Devils are known to attack other creatures in order to take trophies from them.
  - Creature Collection. Belsamaug keep knives and daggers it takes from their victims as trophies. Steppe trolls take the heads of mighty warriors they have defeated in battle, incorporating them into their armor or making the skulls into drinking goblets or saddle ornaments.

Video Games

In Fable you get a trophy for each boss you kill. You can hang them on the walls in your house.
In de Blob2, after capturing the Color Revolution, Comrade Black steals the Prof's Super Wheelchair and uses it for the rest of the game, including in the Final Boss fight.
Immigrant dwarves in Dwarf Fortress might arrive with jewelry made from the bones of creatures they've killed.
In Dragon Age: Origins - Awakening, you get to keep and display in your throne room: the dragon egg from the Silverite Mines, the inferno golem shell from Kal'Hirol, and the dragon scull of the Queen of the Blackmarsh.
After the first fight with Skorne in Gauntlet: Legends, you acquire his helm and gauntlets. Noteworthy in that they are among the most powerful secondary weapons in the game.
Super Smash Bros.. Brawl's The Subspace Emissary has the Trophy Stand, an item that, when thrown, turns weakened enemies and bosses into trophies that you can then pick up and add to your collection.
Diablo II has you fighting in PvP for ears.
Rugal Bernstein from The King of Fighters takes this a bit too literally, as it's revealed in his debut game that he preserves the bodies of the countless martial artists he's defeated over the years by subjecting them to a grisly liquid metal bath, making them living trophies.
Battlefield: Bad Company rewards a player successful in assassinating an enemy in online multiplayer with the knife with their dog tags. This has been included in every Battlefield game released since then.

Web Comics

In It's Walky!, after killing Dargon and taking over his paramilitary organisation, Penny takes to wearing his eyepatch as a personal affect.
Jack Noir, the Big Bad of Homestuck (well, one of them), is expressly fond of doing this. To the point that near the end of his most active arc, he has far more trophies than he can actually wear and has to decide between them.
In The Order of the Stick, Roy takes Xykon's crown and wears it on a string around his neck after "setting him back a bit". This turns out to be a problem when the residual evil on it causes Miko to try and smite him. Xykon takes it back in their next encounter.
- Later, Gannji concocts a plan that requires his partner Enor to kill him, cut of his tail, and keep it so that Gannji can be resurrected later. He tells Enor, 'Tell the guards it's a trophy of your victory. They won't question it 'cause you're part-ogre. They do stuff like that all the time.'
Wespiary Squads in Girl Genius wear over their helmets skulls of Slaver Wasp warriors.

Web Original

Linkara keeps Mechakara's dismembered right hand on his shelf. Bad idea, as Lord Vyce later uses it to take control of Pollo's new body.

Real Life

The British navy tended to leave captured ships with their old name as a reminder that they were captured. If they performed with distinction after capture, a new ship might be built with the same name.
Ancient Greeks often dedicated captured shields and armor to temples. Spartan boys were regularly shown the piles of captured gear at the temple of Artemis.
Headhunting was practiced by Allied soldiers in WWII, much to the horror of the White House. It happened again in Vietnam. Nowadays US military regulations and federal law prohibit soldiers from keeping human remains.
Standards and artillery pieces have long been a traditional Battle Trophy. A regiment used to be considered shamed if it lost it's standard.
The Koh-i-Noor diamond, ended up in the collections of prince after prince after one conquered the other, finally(to date) ending up in the crown of Great Britain.