I have an idea that could go with one of two variations, both may suck:
1.) An object, any old object, with an "effective range." Any and all actions, threats, or even the slightest thoughts of violent actions within the effective range would result in the action being anomalously acted upon the person who did/said/thought the action. Maybe a quote like this would be attached, or, in another direction, it could be a toy with the same effects, plus, it'd occasionally be "picked up" by an undetectable entity. That one would say something like, "Don't hurt her," or "Don't even think of hurting her," on it.
2.) A sword, whenever it is swung, damage appears on the wielder as if they were a person that was right in front of the sword when it was swung.
Am I being confusing? Are these ideas crap? Please answer. :)