Valve has a pretty cool working Team Fortress 2 sentry gun in their office. Well, they can now add the Portal sentry gun to their collection as well.
WETA, the SFX shop behind the Lord of the Rings series and King Kong, produced a life sized working (except the shooting) model of a Portal sentry gun and it is AMAZING! If I had the money, I'd throw it at WETA too to make me one. It's so damn slick and.. and.. I need to win the lotto.