My mom would never hand a knife, a scissor, or anything sharp to another person. You'd have to put the sharp object on a table and let the person pick it up themselves, otherwise is would cut apart your relationship with that person.
Mom had another idiosyncracy (I don't know if it would be considered an old wives' tale) that nobody outside my family ever seems to have heard of.
When one of us kids would fall and bump our heads, she would tape a quarter onto the bump. Supposedly it would keep the bump from getting bigger and would help it go down. I'd be interested to know if anyone else ever heard of doing that or if my Mom was a little off her rocker (kidding)!