agitator

noun3

1. •
   One who agitates; one who stirs up or excites others, for example political reformers.

   • In addition, they kept a watch on political agitators and foreigners arriving and departing at the port. — 1998
2. •
   An implement for shaking or mixing.
3. •
   (historical) One of a body of men appointed by the army, in Oliver Cromwell's time, to look after their interests.