For "weapon":
* Peace pipe: A symbolic object of peace and negotiation.
* Flower: A symbol of beauty and gentleness.
* Olive branch: A symbol of peace and reconciliation.
For "club":
* Feather: Light and delicate.
* Ribbon: Soft and graceful.
* Wand: Often associated with magic or power, but not violent.
For "tool of authority":
* Diplomacy: The art of negotiation and peaceful resolution.
* Dialogue: Conversation and communication.
* Compassion: Empathy and understanding.
Ultimately, the best antonym depends on the specific meaning of "truncheon" in the context you're using it.