Or, how about this one -- "if you return to your hotel room to find you have been robbed of everything except your toothbrush, dont use it"
Basically don't use your toothbrush if anyone who has an axe to grind with you has been near it. My late brother illustrated that about 20 years ago. He got dumped by a girl. He went to her place to pick up some stuff he had left there. He went to the bathroom and did something unspeakable to her toothbrush and took a photo of it being done. Then he left, waited a week for obvious reasons, and mailed her a copy of the photo. He felt guilty about it initially but then find out she was cheating on him and didn't feel so guilty anymore.