Fighter ability

A fighter ability, more often referred to as a passive ability, character mechanic, or character gimmick is an unofficial term used in fighting games, including the  series, that describes special mechanics specific to certain characters (and/or their clones). They can grant said fighter a passive ability, a chargeable meter, extra moves in their arsenal, an ammunition system, or other mechanics that are not directly linked to their standard moveset. In Super Smash Bros. Ultimate, many fighter abilities have a special icon on the character's damage meter and/or a separate section in the character's Move List.

Certain moves and mechanics can be described as a character's "gimmick", but are not strictly fighter abilities due to being too universal or restricted to a single move. Specifically, this applies to the following:
 * Special moves whose function is self-contained, but have their own section in the Move List or otherwise receive special treatment in-game:
 * Special moves that have unique visual indicators on the damage meter or on their model (e.g. Monado Arts, Magic, and Wario Waft).
 * Special moves with multiple names depending on input (e.g. Burning Knuckle / Crack Shoot, Egg Firing / Breegull Blaster).
 * Common properties of hitboxes or universal animations that are simply more prominent in specific characters' movesets (e.g. Pichu's recoil, Marth's tipper, Jigglypuff's self-sacrificial shield jump).
 * Most occurences of armor (however, armor that pulls from a shared resource or that can occur outside of attacks will be listed).
 * Purely aesthetic mechanics, such as Devil Kazuya.
 * Moves that rely on some type of randomness (e.g. Green Missile, Vegetable, Judge, Command Selection, Hero's critical hits on smash attacks).

List of fighter abilities
Game icons indicate that the mechanic was only used in those specific games.

Shared
In addition to the above, certain mechanics and abilities are present on multiple non-clone fighters, but are not universal throughout the roster.

Other

 * In Mr. Sakurai Presents "Pyra/Mythra", Sakurai describes 's Flare Smash as her fighter ability and the counterpart to 's Foresight, and in-game it's also treated as such having its own section in her Move List. However, in practice it's merely a powerful forward smash with long range.
 * In some gameplay footage used in the Mr. Sakurai Presents demonstrations, Ryu's automatic turnaround in 1-on-1 battles seems to be disabled using development tools.