I was about 17 years old and IRC was very hot at the time in school. We had a, for the time, very fast 512Kbps internet connection, and I had gotten used to be able to "ping people out from IRC", no idea why I would do that, but hey I was 17. I was experimenting with ever bigger packets, until I hit something very close to 2^16 but not just.

Until the friendly admin just suddenly stood behind me, tapped my shoulder and said: "If you step away from the computer, let me look at what you did here, there will be no repercussions for doing shit you were not supposed to on a school computer".

Turns out I managed to send a "ping of death" and the network gear in our own school had just died. Internet was so unreliable back then that I just assumed things were a bit slow....