When I was in college, I was leaning on the guy wire of a wooden power pole while chatting with a friend. I was rocking a bit, as I tend to do when standing still, and I noticed that the pole was swaying just a little too. So I tried bouncing the wire some more, and got several inches of sway out of the pole. Neat!

Then there was a loud POP and all the lights on the street went out.

Not sure what happened next, as it seemed like a good time to leave. Moral: don't do that.