Cocoa Beans

Coco bean is a material used in Dye-making, introduced in the Beta 1.2 update. It has a dark brown texture and can be used to color wool. Jeb tweeted that he "removed one of the minecraft dyes." This was presumably the brown dye; however, it hasn't been technically removed, as it's a fully functional item in the game. There's simply no way to acquire it in-game without mods or inventory hacking.