Funny, a lot of abilities people have mentioned here already exist...

Here are a few of my own:

Get on with it: Some characters have annoying Limit Breaks/spells/special attacks that take forever to work. When some fool is standing there, flailing his arms around for minutes on end and glowing brightly trying to cast the Ultimate Super Attack of Doom spell, just use "Get on with it". Your character will turn to the time-waster, whether a friend or foe, and deliver a short but vicious kick to the groin. Instant agony - and 9999 damage - mean that the ostentatious procrastinator is left lying on the ground insensate.

Particularly effective against characters who are trying to use "Blasting Zone", "Super Nova" or the "Knights of the Round".

Vevictis Asmadi: Farts in the general direction of the enemy, and makes unsavoury comments about said foe's mother, causing Poison-elemental damage and shame.

Positively Shocking: Effective against completely stupid enemies. A particularly shiny (and therefore irresistable) fork is placed in front of the enemy, who immediately picks it up. Then their gaze is diverted to the nearby electrical socket, which is also shiny. Insatiable curiosity combines with overwhelming idiocy to casue heavy lightning-elemental damage.

prOOtage: Summons a swarm of Cid's Knights, Administrators and Site Staff who stampede across the screen, trampling the enemy. Followed closely by a similarly large flock of Japanese schoolgirls, whose small yet pointy stiletto heels cause significant loss of blood.