Actually, pen & paper have magical properties, which are probably backed up by some psychology, which is not known to me (yet?). Obviously, things like geometry for games & effects, drawing interface mockups and others involving visual diagrams are much easier to do on paper, but also things like creating project estimates by splitting it in subtasks, writing a list of features & ideas to consider etc - basically creative induction of lists, works better on paper even though you would think computer would be better for it, since you can insert and move around text. It's like when I sit at the computer, my creativity shuts, but when I sit at the paper, it starts flowing.