Check this out.
8 feet long, 150 pounds, and about 35,000 pieces of LEGO coolness! More pictures at the link.
I got the Venator Lego kit for my birthday, which is a good size kit at 1100 pieces, but that monster dwarfs it, and even dwarfs the 3-foot-long Imperial Star Destroyer display-only model.
About a month ago we had the kids out to visit my mother and we took them to the Philadelphia zoo. They had a umber of very impressive LEGO animals on display, the most impressive of which was a life-sized LEGO polar bear. I'll try and dig up the pictures of him.