Neutral NPC's are just that, they mostly comprise of Citizens, and others who have no care for your journey, or what is going on, though some can be convinced to join you, others will attack only if shown hostility.
Arbitrator
Astropath
Bounty Hunter
Dreg
Entertainer
Heavy
Imperial Citizen
Magistrate Elite Guard
Magistrate Guard
Ministorum Priest
Revolutionary
Scum
Servitor - Combat
Servitor Drone
Slaughterman
Skulker
Witch