I usually go with some sort of Caster + Tank + Attacker set up. Caster is in the back row bogged down with materia but has a big MP pool, Tank has the cover materia and Fury to use lots of limits. When not curing uses curing and support materia. Attacker specializes in physical attacks, uses deathblow, added cut, double cut in the order that I get them.

Now that you have gotten me started, I must think up a few more classes.

Samurai
Slash-All (upgraded to Flash to simulate the 'Slash' attack from FF5)
Deathblow
Luck-Plus
Added-Effect + Destruct (on Weapon)
Final-Attack + Leviathan
Enemy Skill w/ '????'

Dragoon (only Cid obviously )
Deathblow + Added Cut
HP Plus
Bahamut
Contain + Elemental (in armor)
Enemy Skills w/ 'Dragon Force'

Temple Knight (Beowolf from FFT)
Contain + Added Effect (on Weapon)
Hades + Added Effect (on Weapon)
Transform
Mystify
Seal
Luck Plus
Luck Plus
Long Range