Summoner and/or Elementalist with Red Magic as second ability. Why?
Simple: Red Magic = Doublecast
Doublecast: Fire Whip + Heavy Dust = fully immobilized enemy
Doublecast+Summons = :o

Doublecast once saved me in a mission. There was a battle with monsters, and a Damage to Animal law. And I didn't have an Antilaw for that. So I used my Elementalist/Red Mage, did only Doublecast: Fire whip + Earth Heal (I like Elemental spells more than White Magic). The second spell was healing, so my actions didn't count as damage.

Selena