My favorite event was the pre-Wrath event when there were undead swarming different spots around the world, and you had to fly around and kill them off and people could be infected and become zombies. 
  I managed to trade a bunch of stuff to the other faction by me and my friend both being zombies. At first they were their own faction, we could trade cross-horde to alliance to get some decent starting wealth and equipment..  
 My favorite lol moment with the zombie event was when a player said "wth is everyone that's a zombie saying 'Braaaaaaains... braaaaaaaains.' That's so lame! Stop it!" (Anything said by a zombie would be heard by a non-zombie as 'brains' due to the faction language translation system.)  
 I haven't had a moment in WoW post-AQ gate opening and post-Wrath event that has sucked me in so completely.  
kavazovangel: 4.3 should be out soon, this or the next month... then probably 4.4 will come, to kill the long wait between 4.3 and the expansion... and maybe another small patch to set things up for the expansion's story. 
  I remember reading a blue post that 4.3 is the last planned content patch before the next expansion. So if they make a 4.4, it'll probably be the set of world events that sets up 5.0.