I don't think delivering electric shock to a finger of a person pressing already lit button would be appreciated. ;)

An elevator hack: Some elevators have kind of "pedal", a movable bar in the floor just by the door. It's normally never pressed, except if something(-one?) gets pulled in, pulling the bar down. Then the elevator immediately stops and all current orders get cancelled. So if you push it with your toe when the door is open on a normal stop, you can cancel all the "queued stops" i.e. if someone made a joke of pressing all the buttons to make the lift stop on every floor on the way...

A normal "legal" cancel button would be handy...