Pixar's Library
Hair rendering always blew my mind.  I remember seeing Monster's Inc in the theater, and the first shot of Sully was when he was asleep in his bed breathing heavily, and you could see the individual strands of hair on his arm flowing back and forth.  I felt the world of animation change right at that moment for me, and now I wait with great anticipation for every new Pixar film that comes out.  For me, "Up" was the only real let-down.