The thing I would go back in to grab (if even at all) would probably be a change of clothes.

I would already have my treasures out (kids, husband, pictures, pets). My insurance/mortgage/stockcertificates/savings bonds/car titles/birth certificates are already in a safety deposit box. I even have some copies of these things at my mother's house. Don't get me wrong I would miss lots of the cool pieces of furniture (that would be hard to replace-due to rarity).
-Summer