Customizer Trennas has devised this fearsome Cecaelian Sea Witch using only official TLG parts. A great selection of parts for the build, and a female to boot (we don't see enough of these I'm afraid).
The posing of the arms provides motion and depth, and the camera angle gives a great sense of action (although it does remind me a little of the 1960's Batman series).
More of this great build and other custom creations can be seen on Trennas' Flickr stream.