A Signature Device is a tool, weapon, or object that all members of a certain group (usually Differently Powered Individuals) possess and marks them all as similar in some way.
Most stock costumes include some, generally examples of Truth in Television. Particularly:
- Scrubs, stethoscopes and clipboards for doctors
- Guns and badges for police officers
- Cellphones, PDAs or headsets for businessmen
Compare Mark of the Supernatural.
- In Attack on Titan, members of the Survey Corps have the 3D Maneuver Gear and the dual swords. The intro demonstrates the Gear in action just to drill this in. (3D Maneuver Gear allows the user to get airborne at a moment's notice - useful given they fight giants that can only be killed by cutting out the back of their necks.)
- The Zanpakouto in Bleach are unique blades weapons that all shinigami, Arrancar, and Visoreds use.
- The Diaries (of all sorts from phones to coloring books) in Future Diary, are used by the 12 Diary holders to compete in a battle royale competition for who becomes the next god. Each Diary tells the future in a unique way based on their owner's personality.
- In Eden of the East, each of the Seleção is given a distinctive cellphone which connects them to the concierge service to execute their commands and serve as a credit card. They are each numbered from 1-12.
- Fullmetal Alchemist: State alchemists have standard-issue pocket watches, which are often used to identify them as such.
- Naruto: Almost every shinobi wears a headband with a metal plate, engraved with the symbol of the village they represent. These can be taken away when someone dishonors their place as a ninja, and not wearing one is seen as disrespectful.
- Soul Gems in Puella Magi Madoka Magica are Soul Jars that the magical girls obtain after agreeing to the Magical Girl contract Kyuubey offers. They have to maintain its purity lest it turns dark with corruption. Unfortunately, corruption is inevitable, and in fact the Soul Gem is designed to eventually go corrupt.
- The transformation wands from Sailor Moon, which are used to activate a Sailor Guardian's Transformation Sequence.
- Tiger & Bunny: Each of the heroes that work for Hero TV have similar comm wrist bands that alert them to emergencies to respond to during their off time.
- Every incarnation of has a form of Duel Disks, a device worn on the arm that allows the wearer to play Duel Monsters with the full holograms-and-LP-counters trappings no matter where they are. The original introduced them in the Battle City arc, and they proved so convenient that they became de rigeur for later installments.
- Yu-Gi-Oh! 5Ds has the Duel Runners, which are... well, the fandom meme is "CARD GAMES ON MOTORCYCLES!" for a reason. It's possible to detach the dueling part from a Duel Runner and use it as a Duel Disk by itself, but most of the dueling in the series is done in motion.
- The spell books from Zatch Bell! are used by Mamono owners to command their mons in battle. If the books are destroyed, the Mamonos are banished back to their home realm.
- Star Wars: Lightsabers indicate that a wielder is a Jedi or force-sensitive, and red ones specifically indicate a Sith.
- Doctor Who:
- The sonic screwdriver, first introduced in "Fury from the Deep", quickly became the Doctor's go-to trinket in almost all of their incarnations. The only Doctors that lacked the device on-screen were the First and Sixth Doctors — the former because it didn't exist yet, the latter because the sonic screwdriver was temporarily retired midway through his predecessor's run before coming back at the very end of his successor's.
- The Tissue Compression Eliminator served as the Master's signature weapon in the Classic Series, tying in with his nature as ruthless, yet plagued by a cartoonish Complexity Addiction, thanks to its gimmick of fatally shrinking people down to the size of action figures so that he can leave them as calling cards. The TCE is so thoroughly associated with the Master, in fact, that both the Peter Pratt and Anthony Ainley incarnations first made themselves known by leaving shrunken corpses lying around for the sake of a Wham Shot. It made a return in the New Series, with Sacha Dhawan's incarnation announcing his true identity with the shrunken body of the real O.
- Pretty much every Starfleeter on Star Trek will be seen using a tricorder at some point. This is because Starfleet is all about science and exploration, and tricorders are powerful scientific tools.
- Assassin's Creed: The Assassins will almost always be seen wielding their Hidden Blades, a weapon used since the very inception of the Order. Every non-Assassin who wields one was either gifted the tool, forcibly obtained it from an Assassin (whether through stealing or as a battle trophy), or happens to be a turncoat from the Order.
- The Belmonts from Castlevania almost always have the same set of secondary weapons: throwing knives, throwing axes, cross, holy water, and stopwatch. Even moreso, all Belmonts wield the whip Vampire Killer. Allies will wield all sorts of weapons though.
- Keyblades in Kingdom Hearts, key-shaped swords used by the protagonists that can open and close any lock, whether literal or metaphorical, and can only be wielded by those with strong hearts.
- Poké Balls, which are used to catch the titular Pokémon and the Pokédex, which is a digital Pokémon encyclopedia for the Pokémon trainers, or at the very least skilled and/or important ones. Receiving one at the beginning of the game indicates you're now a trainer.
- Gym badges also indicate someone is taking the gym challenge.
- Player Pins for Players in The World Ends with You mark them as players of the Reaper's Game trying to win and be revived.