Eating raw cookie dough will give you worms. (I think this was my mother's way of just keeping us out of it! )
Eating carrots is good for your eyes.
Keep making ugly faces and your face will freeze that way.
If your right hand itches, you'll meet someone new.
If your left hand itches, you're coming into money.
If your ear itches, someone is talking about you.
If your breast itch, someone is craving your company.
I'm sure I can think of a million more.