Sorry If this is a repost but I couldn't find it anywhere.
Okay to kill guards of your own faction(I haven't tried alliance yet) create a new deathknight and get it out of the starting area but do not turn in the quest Warlord's Blessing.
From now on the guards in Orgrimmar with throw shit at you and be sort of hostile but you can't use any abilities. Level your Deathknight to 85 and you can use Outbreak and Dark Simulacrum on them and actually kill them. I suggest getting a healer as they do fight back.