I can be a pack rat, but I don't really hoard anything in particular. I just get lazy and toss old junk in the basement, and I have a tendency to keep anything that I feel may have some value in the future. The only exceptions may be items from my childhood, mostly things that hold no market value but hold too much value to simply discard. This includes things like the old NES and Dreamcast. It once included the ColecoVision, but I do believe that has *some* value on the used market now.
FWIW, I do tend to keep boxes. I've resigned myself to throwing out boxes for most things, but I keep boxes for most electronics. This includes the huge box for the plasma TV, for my speakers, my receiver, dvd and bluray players, etc... For the bigger, more expensive stuff, it's more because there's nothing like the original box for transport. For less expensive things like the blu-ray players that could be packed easily otherwise, the original boxes are so small that I figure I may as well keep 'em.