My favorite unsend gag was the IBM commercial about the two ticked off employees who were in process of writing a flame to their boss about the crappy laptops they had. Just as they hit send, two new Thinkpads arrive for them. They look at each other for just a second, and then frantically start saying "UNSEND, UNSEND!!!" as they hunt the screen for the button.

Another solution to the unsend button (and one I've used before) is to go into the bosses mail queue and edit out the message by hand before shem gets it. Of course it helps to be root to do this, but it's not absolutely neccesary.