Quests
Know Your Lore: Welcome to the machine
What I really enjoyed about Welcome to the Machine is that for a moment it took you out of that role of adventuring hero, and put you in the NPC position. It was an amazing, wonderful, weird quest, and I still consider it one of the highlights of the Cataclysm expansion. As much as I love the quest, though, I didn't really want an entire expansion of it.