Barn Door Plank
This item could be obtrained from the drop system. It was released a couple of days before the Pyromania Update in June 2012. After the update, the Barn Door Plank was incinerated and renamed to 'Incinerated Barn Door Plank', thus becoming a crafting ingredient for a 'Pile of Ash'.
Barn Door Plank
Team Fortress 2 Level 1 Plank
This barn door plank doesn't look mysterious at all, until you view it at an atomic level. Hey, there's a horse there next to all those atoms. They're taking turns riding the horse. Man, how did a horse get there? Pretty darn mysterious.