The Phantom Vs. Aliens

H.R. Giger's  Alien is rightfully one of the all time classic monster designs,  There are so many great elements to it, from the spiked tail, to the way it can curl up and hide in the ceiling, to the double set of teeth.  What really put it over the top for me, though was what he didn't include.  The lack of any discernible eyes was a very interesting choice, and really freaked me out.  It just adds another element of fear when you don't know where the creature is looking.