M-x spook adds a line of randomly chosen keywords to an outgoing mail message. The keywords are chosen from a list of words that suggest you are discussing something subversive.
The idea behind this feature is that the suspicion that the NSA snoops on all electronic mail messages that contain keywords suggesting they might be interested. (The NSA says they don't, but that's what they would say.) The idea is that if lots of people add suspicious words to their messages, the NSA will get so busy with spurious input that they will have to give up reading it all.
Here's how to insert spook keywords automatically whenever you start entering an outgoing message:
(add-hook 'mail-setup-hook 'spook)
Whether or not this confuses the NSA, it at least amuses people.