Of course if none of the above suggestions suit you, you could try running off screaming and hollering and throwing a big hissy fit. This might make the other party wonder what it was that they did wrong to upset you so bad.
I was just seen again by the neighbor across the street. I was watering our privacy trees and moving the hose. I was standing there watching the rate at which the water was coming outta the hose and noticed movement and looked up. He was on the roof of his house looking down into our side yard. He smiled and waved. I smiled and waved back and then he went about what he was doing. I didn't duck for cover, crouch down or shield myself. I just stood there natural and smile and waved. After times like that ... I'm thankful for the cool neighbors we have. ;-)