EXP bonus abilities

Level Up, also known as Level Lust, Exp Up, EXP Up, Double EXP, Knowledge to Power, Accrue EXP, Smart Valor, Gained Exp UP, is a support ability, mostly found on pieces of equipment, namely accessories, that usually doubles the amount of experience points a character earns from battles. It is an ability usually acquired around midway to late in the game.

Final Fantasy IV
Level Lust is an ability gained from an augment found in the Hummingway Home in the game's Nintendo DS version. It is a support ability that increases the amount of EXP gained from battles by 50%. It can be obtained multiple times via the New Game Plus feature.

Final Fantasy V
EXP Up is a Level 2 ability found only in the Advance version, and is part of the Cannoneer class. The ability allows characters to gain 1.5x more EXP after battles, and requires 150 ABP to master.

Final Fantasy VI
Double EXP is an ability found in Growth Egg, which can be equipped by every character. It doubles the amount of experience gained from battle. It can be found inside Darill's Tomb, in a hidden room after completing a puzzle. It can also be obtained from the Coliseum by betting a Tintinnabulum, or morphed from Vasegiatta, Marchosias, and Galypdes.

Final Fantasy VII
Level Up is an ability found on the EXP Plus Materia. At Level 1, it increases EXP earned by x1.5, and at Level 2, by double. The EXP Plus Materia can only be obtained after Meteor is summoned at the Gold Saucer's Wonder Square, for 2000 GP. The effect doesn't stack.

Final Fantasy IX
Level Up is a support ability learned by everyone. It is learned through Iron Helm, Egoist's Armlet, Fairy Earrings, Pearl Rouge, and Rosetta Ring. It increases the experience earned by 1.5, rounded down.

Mastering this ability requires 75 AP for Zidane, 30 AP for Vivi and Dagger, 50 AP for Steiner and Amarant, 40 AP for Freya, 60 AP for Quina, and 65 for Eiko. Seven Magic Stones are needed to equip it.

Final Fantasy X
Though there is no EXP and therefore no EXP multiplier in Final Fantasy X, there are various AP multipliers, including the weapon auto-abilities Double and Triple AP, and the Overdrive → AP ability which gives the player AP instead of filling up the Overdrive bar.

These can be customized into weapons by using 20 Megalixirs, 30 Winning Formulas and 10 Doors to Tomorrow for each ability respectively.

Final Fantasy X-2
Double EXP is an ability found on the Lady Luck dressphere mastered for 80 AP, and Covenant of Growth Garment Grid by passing through the yellow gate.

Final Fantasy XII
The party can double their EXP intake by equipping the Embroidered Tippet accessory. It can be found in a chest in the Babbling Vale of the Mosphoran Highwaste after reaching the Phon Coast, stolen from the Coeurls on Tchita Uplands, or bought from Old Archades for 5,000 gil.

Final Fantasy XII: Revenant Wings
Knowledge to Power is an ability learned by Ashe that increases the amount of EXP gained for the whole party, and is learned from the Embroidered Tippet accessory. How much the accessory increases EXP intake appears to depend on the battlefield.

Final Fantasy XIII
CP x2 is an ability granted by the Growth Egg, a reward for mission 55. It grants the whole party double the amount of Crystarium Points normally won in battle.

Final Fantasy Tactics
Accrue EXP is an ability that allows a character to gain EXP as they move. It is learned from the Arithmetician class for 400 JP. EXP Boost, also known as Gained EXP UP, is a support ability learned from the Arithmetician job for 350 JP. A unit with this ability will receive 1.5x the experience from every action they perform.

Final Fantasy Type-0
Growth Egg, which can be acquired from the demo version and by completing a sidequest in the town of Bazz, gives a character 2x EXP. Mog's Amulet gives EXP x4 ability but can be acquired only in the end of multiplayer mission if it was ranked S. Additionally, each character has a weapon with the 2x EXP, which can be obtained through the multiplayer SPP shop. In the PSP version, all of these accessories could also be obtained by redeeming tickets through the Square Enix Members Site to transfer into the game. The effects of support abilities stack, making it possible to get a maximum of 16x EXP on one character.

Final Fantasy Crystal Chronicles: Echoes of Time
Smart Valor slightly increases the amount of EXP the user gains from defeating enemies, and can be customized onto equipment through the Extreme Mania jewel.

Bravely Default
Experience Up is a support ability learned by Conjurers at job level 14 (max). It allows the character to earn 50% more experience than normal. The Growth Egg accessory also doubles the amount of EXP and JP earned at the cost of 0 pg.

Dissidia Final Fantasy / Dissidia 012 Final Fantasy
The three Chocobo accessories Chocobo Down, Chocobo Wing and Chocobo Feather offer 20%, 50% and 100% bonuses to Exp earned in battle. The Growth Egg increases Exp earned by 20%, and the Excalibur II increases earned Exp by 100%.

Three abilities learned at Level 100 convert earned Exp in battle into HP, Bravery or EX Force, depending on the ability. In Dissidia 012, Exp to HP and Exp to Bravery are learned at Level 99, while Exp to EX Force and the new ability Exp to Assist are learned at Level 100.

Theatrhythm Final Fantasy
EXP Up is a special ability with three levels of power, each level increasing the HP earned in battle by 20%. No character learns any version of EXP Up normally, they can only be learned by usage of the EXP Up Scroll items.