What are weird non-biblical rules you've heard some religious people make up and follow?

I was talking to a friend about World of Warcraft. I asked him if he wanted to start a horde character with me so we could level up. He got really tense and said “I can’t play the horde. I’m Christian.” He said true Christians would only play the Alliance side of WoW as it’s obvious that they are the “good guys” and the horde are the “bad guys.”

I understand that there are rules I don’t always agree with or understand, but if they have a biblical basis – even one from a verse that I think is misinterpreted, I try not to judge. But I am pretty sure that Jesus doesn’t give a hoot about what you play in WoW.

Anyway.. have you heard any weird totally nonbiblical rules someone made up in order to feel more spiritually correct?