Either a Gambler or Dragoon or ninja.

While I like the natural speed abilities of a theif, I don't like their (normal) lack of attack power (unless we're talking about Locke who can basically be a theif/warrior).

Gambler has the whole game thing so that makes up for the lack of power aspect to me.
Dragoon's are just... overpowered so that is always a good thing.
Ninja? Seriously, if the ninja skills would work like Shadows, all I'd have to do is have 99 of the current best weapons and hit every monster for like 3000 damage with each throw. xD

... So prolly a ninja. A ninja gambler!