try some of these combos
WEAPON : Ultima-MP Absorb, Ultima-HP Absorb, Ultima-Sneak Attack,
ARMOR : Ultima-MP Turbo, Ultima-Quad Magic, Ultima-Final Attack
WEAPON: Knights of the Round-MP Turbo, Final Attack-Phoenix, Master Summon-MP Absorb, Elemental-(Your favorite elemental summon)
ARMOR: Quad Magic-Hades, Sneak Attack-Choco/Mog, W-Summon
ARMOR/WEAPON : Master Magic, W-Magic, MP Absorb-Master Summon, MP Turbo-Knights of the Round, Master Command, Enemy Skill, W-Summon, Slash-All, Mega All, HP Plus, Final Attack-Phoenix
WEAPON/ARMOR: Enemy Skill(Big Guard), Mime, Final Attack-Phoenix, MP
Turbo-Knights of the Round, HP Absorb-Master Summon, Underwater (If facing Emerald WEAPON), HP Plus, Master Command, Master Magic-Quadra Magic, W-Summon, W-Magic, Mega All
WEAPON/ARMOR: Quad-Magic-Fire, MP Turbo-Fire, MP Absorb-Fire, HP Absorb-Fire, Added Cut-Fire, Added Steal-Fire, Magic Counter-Fire, W-Magic, Magic Plus
(This one can be used with any materia, you can use comet or ultimate with it if you want, but it seems that when ever I cast the spell, the game would somehow freeze, the caracter will stop attacking, the enemy wont do anything, the camera will keep moving and do the caracter and opponent, no one will ever attack, if you have a timer, it will keep going down without you being able to do anything about it)