The Pin Is Mightier Than the Sword

For some reason, it's common for badges to be depicted as either giving special abilities to or augmenting the special abilities of the wearer. This could be rooted in the fact that military officers and the like wear them as symbol of authority. However, it seems that users of these badges don't usually have much authority.

This trope is common in RPGs, where they will be collected as equipment.

Subtrope of Clothes Make the Superman.

Has nothing to do with using sewing needles, tacks, pushpins, or the like as weapons.

Anime

 * In Bleach, Ichigo has badge that can, among other things, detach his soul from his body.
 * In Sailor Moon the main character has a brooch which serves as both a Transformation Trinket and a holder for her Power Crystal. Chibi-Chibi also gets one later on.

Literature

 * E.E. "Doc" Smith's Lensman series. The Lens, which is the badge of the Lensmen of the Galactic Patrol, gives the wearer a variety of useful mental powers, including language translation. It will also kill anyone who touches it other than its owner.

Tabletop Games

 * Dungeons and Dragons: Forgotten Realms. In 2nd Edition, Harper pins give their wearer a bonus to defending against Mind Control attacks and immunity to any kind of detection spells/psionics, Magic Missiles and electricity/lightning attacks.
 * In Voltron, the keys to the lions hide themselves as pins.
 * In Voltron Force, the keys are required to activate Voltcoms

Video Games

 * In Earthbound (and the other Mother games), one of the earliest really useful special items you get is the Franklin Badge, which reflects electrical attacks.
 * In Final Fantasy Tactics Advance, certain characters wear a ribbon (the military style, with a badge) that makes them exempt from all laws.
 * In the Mario RPGs, badges affect stats and sometimes have more interesting effects.
 * The World Ends With You is built around this trope; every "player" in the "game" the protagonists are trapped in gains Psychic Powers from one. Neku, the Player Character, is unique in that he can use more than one (thus he can use pins in a Powers as Programs style). Oh, and the Big Bad's Evil Plan is
 * In Pokémon, badges obtained by defeating gym leaders have special effects.
 * Many of the trinkets in World of Warcraft fall into this category, although it's hard to tell with some of them because their names are so vague.