I picked shape. Mostly it's because shape is something I can appreciate on many levels--mentally, visually, tactually--whereas the others kind of elude me in some ways. My brain isn't oriented as well for numbers as for words so weight is sometimes vague for me and size almost always has to be a comparative thing: not something I just appreciate on its own. That said, like many people, I do like size comparisons. Still, overall, it's shape to which I find myself most attracted.