AP bonus abilities

Ability Up, also known as Double AP, is a recurring ability in the series which doubles, or in the case of Triple AP, triples the amount of AP earned from battles. The ability didn't appear until Final Fantasy VII, and is a rather rare ability at that.

Final Fantasy VII
Both Double AP and Triple AP make their debut here, and only on equipment. Double AP can be found on the weapons Force Stealer, Rune Blade, W Machine Gun, Drill Arm, Powersoul, Motor Drive, Platinum Fist, Wizard Staff, Wizer Staff, Plus Barette, Magic Comb, Twin Viper, Wind Slash, Rising Sun, Peacemaker, Buntline, Black M-Phone, White M-Phone, Javelin, Viper Halbred, Platinum Bangle, and Rune Armlet. Triple AP is only found on Scimitar and Apocalypse.

Final Fantasy IX
Ability Up is an ability that all characters can learn which doubles the amount of AP they earn after battles. The ability can be learned from Stardust Rod, Green Beret, Diamond Gloves, Brigandine, Silk Robe, Diamond Armor, Cachusha, Lapis Lazuli, and Ribbon.

Final Fantasy X
Double AP, Triple AP, and Overdrive -> AP are all abilities that can be found or Customized onto weapons. Overdrive -> AP transfers what would fill up the Overdrive gauge for a character into small amounts of AP that character earns after battle.

Final Fantasy X-2
Double AP appears only on the Covenant of Growth Dressphere by passing through the blue gate, while Triple AP only appears on the accessory AP Egg.