My Gran would tell us that if you put your shoes on the table, you will die with your feet off the ground.
I think that refers to hanging.
My own personal superstition is that I never put my crash helmet on the ground upside down, so that the painted surface touches the ground. I don't want it to get used to being like that in case it does it while I'm wearing it.
I also think that new guitars don't know any songs, so I have always bought second hand ones. Though there is an explanation for that which is at least semi rational!
Cheers
Dave