The Daily Grind: What's the worst in-game mistake you've ever made?

We've all been there, right at that moment. You know the one -- when you miss-click, when you aren't paying full attention, when you say something you shouldn't, when you turn right instead of left. Suddenly, your eyes widen, stomach drops and mouth goes dry. You've made a terrible, terrible mistake. And we want to know all about it!

So let's engage in a bit of virtual therapy today and get our worst in-game mistakes off our chests (sorry, no "It was a mistake to sign up for such-and-such MMO" comments needed). Trudge up memories that you thought were long forgotten, and share with the group what horrific misjudgment you've made in the past. Did you accidentally sell an incredibly rare piece of loot to a vendor? Did you delete the wrong character on the selection screen? Did you go /afk just a little too long and come back to find that you just wiped your entire raid? What in-game mistake made you stand up, slap your forehead and shout "D'OH!" loud enough for the neighborhood to hear?