Check out this email footer over on SHG's page...it's a good one. Here's one I used to use, but now I am tired of:
This email is intended for the use of the individual addressee(s) named above and may contain information that is confidential, privileged or unsuitable for overly sensitive persons, or those with no sense of humor and/or irrational religious beliefs. If you are not the intended recipient, any dissemination, distribution or copying of this email is not authorized (either explicitly or implicitly) and constitutes an irritating social faux pas. No animals were harmed in the transmission of this email, although the ferret next door is living on borrowed time, let me tell you.
And here is my current one:
Dissent is the highest form of Patriotism