The Lady Bird over on WoW Ladies posted about a quest I've heard about but never done before. It's the Sully Ballou's Letter quest-- it starts from a poor deceased dwarf that you can find in the water beneath the Thandol Span (that's the bridge just north of Dun Morogh). In his hand, there's a letter that you can read, and that needs to be delivered to a woman in Ironforge.
Lady Bird read the letter and found it suprisingly emotional, and then found out the reason for that is because it's real-- it was written by one Major Sullivan Ballou, directly before the Battle of Bull Run in the Civil war. It was famously read in Ken Burns' Civil War documentary, and the full text of the original letter is also available online. It is pretty darn touching, both as a love letter, and as a meditation on what real life war really costs us, both for those directly involved, and for those waiting at home for them to return.
Blizzard has put a lot of hidden gems in this game, of course, but this might be one of the most touching.