Alone w/ endgame equip: Samurai's pwn big and bad. Lotsa HP, lotsa DMG, lotsa Def, great ranged attacks and support skills. Make it a female for even better ranged attacks.

Alone w/o endgame equip: Monk or Lancer for all reasons mentioned above.

As part of a team: Mime, no question, no arguement, they are the ultimate teammate.