This LEGO build of Smaug from The Hobbit (not modeled on the movie specifically) is suitably imposing to look at. Its creator Shawn Snyder says that the model is 28" from head to tail with a 35" wingspan. It is intended to be used as part of a larger LEGO diorama of Smaug's attack on Lake Town (Oops! Spoilers for a 77 year old story!).
For all that I think its an impressive model in its own right.
Source: Flickr - Smaug