One day, about a year ago, I was grinding for Argent Dawn rep in the Plaguelands. I downed a Crypt Fiend and it dropped a Hanzo Sword. While not particularly valuable, it was the first BOE blue I had looted in months. Happy with my find, I kept on grinding. Not twenty minutes later, on yet another undead mob, I looted an Orb of Deception! Now this was worth something! On Bloodhoof it was selling for upwards of 500 gold at the time.
About an hour later, a couple guildies needed help finishing Stratholme. I was in the area, so I headed off to the instance. On my way, a plaguehound and one of those annoying bats knocked me off my mount. Instead of running, I went ahead and killed them. Good thing I did, as the plaguehound dropped a Glowing Brightwood Staff. To this day that is the only BOE epic I have ever looted outside of an instance. In fact, I don't think I have found a single valuable blue since that day either.
That was far and away my luckiest day in WoW. What's your luckiest day? Ever walk out of MC with 5 new epics? Find an amazing pricing error in the auction house?