sight -opens the Map
silence- Causes mute, which prevents the casting of magic
teleport- takes you out of the dungeon
protect- raises defense
reflect- reflects magic on the enemy (This includes white magic)
blink- makes you difficult to hit with physical attacks
esuna- cures status problems
meteo- does a hell of alot of damage
mini- inflicts mini status
piggy- inflicts pig status
bio- does poison damage

That's the ones I remember, though feel free to correct me if I'm wrong.