I've tried this in Orgrimmar, but assume it'll work in other cities, and for the alliance too.
In Org near the flight tower, there should be a Cenarion Circle representative, if you declare war on CC and attack him (don't kill him, just kite him around enough so he stays on you) any guard that pats next to you will constantly bug out and follow the CC rep around.
While doing this, they ignored a few of my Alliance friends that were standing next to them, and when they tried to attack the guards, they said they were evading.
Useless?
I guess.