Gladiator can become broken with a little luck (it does 9999 damage if the character hits something that doesn't absorb their element with a critical iirc). It's pretty nice before you get Rapid Fire/Dual Wield/Spellblade.

I love Oracle, just for their Read Ahead which practically gets rid of random encounters.

I never really used Cannoneer, since Chemists were already useful enough.

Necromancer is awesome but by the time you can obtain it becomes Awesome But Impractical.