Jedi Knight: Human, or Mirialan. (Mirialan is my personal favorite, her voice fits well with her face.)
Jedi Consular: Miraluka, Mirialan, or Togruta.
Trooper: Human.
Smuggler: Twi'lek, or Human. (Twi'lek personal favorite, same reasoning as Mirialan. It also just makes sense.)
Sith Warrior: Sith Pureblood, or Human.
Sith Inquisitor: Twi'lek, or Human.
Bounty Hunter: Human, or Cyborg.
Imperial Agent: Human, or Chiss. (Chiss is my ABSOLUTE favorite.)