I know you will find this very difficult to believe, but, I hoard Mountain Dews. I know, I can hear your shock all the way on the east coast.
I would have to say photos. I moved about 6 months ago and am finally unpacking the last of the boxes. I have two cartons of loose photos, one carton of photo albums and two more cartons of framed photos. Not to mention a few thousand digital ones saved to various hard drives.