Module Meme: Which of Your Modules Has Taken the Most Use and Abuse?

I was referencing X1 this morning trying to remember how the rope bridges were treated on the Phanaton platforms, and it struck me... "no matter how much care I tried to take of my stuff, I still have poor bastards like this one." The cover's come apart, and the last page (the one with the hex map for the players to fill in) is missing. It's not all marked up like my copy of Keep on the Borderlands, but Id rather have scars than missing limbs any day.

I'm sure the missing hit points from this copy of The Isle of Dread are only flesh wounds by comparison to some of your stuff. So... which of your modules (or sourcebooks, for that matter) has taken the most use and abuse? And as a visual person, I think it's cooler to show than tell.