Signature Trait

A Signature Trait -- sometimes called "a gimmick" -- is a feature that distinguishes a character from the competition (with strong connotations of not adding any functionality or value). The sheer power of such a trait, when properly used, cannot be underestimated; a properly executed Signature Trait can make a character truly memorable.

The true definition of a Signature Trait is if an Alternate Universe or Continuity Reboot equivalent (or a Captain Ersatz) isn't "really" that character without the trait, then that's this.

Most common in Comic Books and Professional Wrestling, but can show up elsewhere. See also Idiosyncrazy, for when a character's Signature Trait is driven by his insanity, rather than out-of-universe considerations.

Because this is also called a "gimmick" it is not to be confused with Gimmick, a trope about encrustations added to a work in the process of overhyping it.

Comic Books

 * Batman's Signature Trait in the Justice League is either his detective skills, or his sheer intellect.
 * He's also The Cowl in a team of Capes.
 * Batman's Rogues Gallery is filled to the brim with these. To name some particularly famous cases:
 * The Joker provides an example of how far you can go without going outside your Signature Trait: outside of the Silver Age, he defines the human version of the Complete Monster Monster Clown. Within the Silver Age and Silver Age styled settings, he's merely a prankster Villainous Harlequin.
 * The Riddler, in some versions, is actually an interesting case, in that his trait is also explicitly his motivation and downfall: His superiority and inferiority complexes are such that he has to leave clues, to prove that he's smarter then everybody else.
 * Most Batman villains are like this to either a small extent (Catwoman is fond of going after cat-related valuables) or a huge extent (the Riddler as previously mentioned). Appropriately, Two-Face can't seem to decide whether his theme is opposites or the number two. Maybe he should just flip for it.
 * Toyman is an excellent example of a character whose only real continuity between versions is his Gimmick.
 * An example of a poorly implemented Signature Trait: Paste-Pot Pete. (Pete later changed his name, because it was too silly, even for the Silver Age.)
 * Spider-Man's gimmick, in universe, is his spider theme (less important) and sharp wit (more important); but out of series, his gimmick is One of Us: he's an average person who got hit with the superpower stick, and now has an extra set of responsibilities.
 * Captain America's gimmick is Patriotism and embodying the American Fighting Spirit.
 * Green Arrow has a whole Robin Hood and Bow And Arrow gimmick going.
 * As well as his very outspoken left-wing political views, which, since the '70s, have been a defining character trait of his.
 * The Flash's Rogues Gallery was full of gimmick themes with obvious names: Captain Cold, Heat Wave, Captain Boomerang, Mirror Master, Rainbow Raider, The Top (In that he spun like one).
 * The Punisher's willingness to kill and torture bad guys.

Literature

 * Nero Wolfe was best known for solving cases while never leaving his house. His narrator, Archie Goodwin, did all of the relevant legwork; the combination of the the Hard Boiled-styled detective and the very Defective Great Detective was the gimmick of the series as a whole.

Professional Wrestling

 * Jake "The Snake" Roberts, whose gimmick was being a Complete Monster. And having a snake.
 * However, he may end up being just as well known for his born-again Christian gimmick in the 90s, as it led to Stone Cold Steve Austin delivering his Austin 3:16 promo, and the Attitude Era at large.
 * Prolific in the late '80s and early '90s WW F E, when every character would be gimmicky. See Wrestling Doesn't Pay for examples.

Video Games

 * Monster Rancher differentiates itself from other Mons Series in that you can create monsters to raise by "unlocking" them from CDs or DVDs that you already own.