Viera are my favorite. Good range of spells/skills, job variety. Assassin's shooting Ultima from range with a bow is always a ton of fun; I just wish I could change their outfit color to red (any Fate/SN fans out there?). Summoners, Elementalists, Spellblades, there's just too much to have fun with.

Bangaas are a close second. Good-old-fashioned bangaa muscle can also be a lot of fun, but I also like how there are actually female bangaa in the FF universe. I don't remember ever hearing of female Seeq, Nu Mou, or Moogles.