Unruly Passengers

How would you handle a situation where a paying passenger began to
manhandle the controls?
What would you do if a passenger keeps interrupting you during a
single pilot IFR approach into a very busy airport?
What would you do if your passengers lit up their marijuana in the
back of a twin?
What would you do if the passenger was so big they kept getting in the
way of control travel?
What would you do if your passenger decided to get out of the airplane
while in flight?
These are all real and all have happened to me in my 45 years of
flying. A lot more that I can't think of at the moment.
A pilot was recently faced with it when an 84 year old man decided to
unstrap and get out of the front cockpit of a biplane and plunged to
his death. The pilot was unable to stop him.
What would you do?