Every world needs a few crazies. You can call them whatever you want. I'm calling them zealots because it's Z day. Zealots are people who are incredibly invested and enthusiastic about something (or who belong to a certain sect of Judaism like Judas Iscariot).
What are your zealots zealous about? How does that help to define your world? I think you can say a lot about a world just by depicting a people who are zealous about something in that world.