Clackers, Poppers, Wrist Knockers
I have been a fan of these wonderfull toys ever since were invented.

I still can't believe they were banned! I used to play with my knockers for hours on end. Sure they could leave a nasty bruise but only if you did it wrong. The biggest danger was when cheap or home made ones would explode. We rarely wore safety glasses. I had a brand new one that broke the other day. That might be because it's 40 years old.