Tipsy passengers
I would have (and have had!) no qualms in denying access to a drunk passenger, regardless of how much they had paid out for the flight. However, there are degrees of being drunk, but it is sometimes hard to discriminate between somebody who has had a few too many but is in complete control of his faculties, and one that will act up during the flight.
If you are going to climb to a reasonable altitude during the flight, remember that the pressure change and the slight reduction in oxygen levels will have an adverse reaction on somebody who is only "slightly over the top" at ground level....
If you ever suffer the effects of a drunk throwing a fit during a flight, I'm sure you will think twice before letting one on your helicopter.....it's your life and that of your passengers that is at stake!