Custom Race 1 (Fighter, Four Armed Axenado)
Duergar 1 (Barbarian)
Half Orc 1 (Fighter, Part Elf, Human, and Orc, using the rules in the back of Bastards or Golarion)
Ratfolk 1 (Rogue, no ranks in Sleight of Hand, wields a light shield)
You could also take the Adopted trait and choose multiarmed. At my house it stacks with a race that already has Multiarmed.
Having six arms and taking the multi-weapon fighting and dual wielding extra attack feats as well as using speed weapons grants 30 attacks on a full attack action.
