First off you need to be a Night Elf Hunter. Also helps if you are REALLY bored. Go to the Barrens and tame a low level monster. With your tamed monster go near the entrance of the Crossroads and Shadowmeld. Low level Hordes won't see you and they will attack your pet thinking it is a mob, thus causing them to be flagged.
Have fun
Another thing to do is go AFK and turn PvP on.
Low lvl's will attack you without a doubt.
Very fun to wipe a low lvl group on your own!
(Both of the above are mean I admit....but funny, so its ok. )