The description of various subversive cluster naming schemes is a close runner up. Next time I'm setting up a cluster, I must remember to name my machines up, down, crashed, rebooting, etc. I miss devnull.
Neither of those compares with the last networks lecture, where in the process of trying to explain masquerading attacks, Prof. B went on a long, involved, and very through explanation of how to set up and exploit a fake ATM. Included were details such as the best spots for them to go undetected (strip malls), how to collect and verify PINs, and how to read a magnetic stripe.
Someone asked him how he knew all this, at which point he deflected the question with the sheer power of cool from his knowledge of the technical specs of Blue Gene. Such neat stuff. I wish he had any interest at all in security.. I'd love to work for this man, but all he wants to do is fine tune his supercomputer and go to conferences :-P.