Not really a puzzle, but I think some people here might still be interested in this:
Today was Halloween, and to celebrate the occasion I made a life-sized (at least, based on the Lab Rat comic) Weighted Companion Cube and carried it around with me in school while dressed up as Doug Rattmann.

The base was made from six 16inx16in sheets of cardboard taped together in to a cube, and then completely covered in duct tape. The corners and edges (and the hearts!) are made of cardboard, spray painted and duct taped on. I am aware that it is missing the pink stripes dividing the cube like a 2x2x2 but I couldn't find any masking tape to paint pink. I didn't think to take any progress pics since I didn't have a reasonably sized lens at hand, but I do have one picture of just the cube with four corner plates placed on it below.

Hope you guys like this!

Very nice!

Ah! Portal is awesome.

You could have downloaded a 3D model and had it printed on Shapeways. Then it would certainly have been weighted (although your bank account would have been lighter)