Just had to stick a post up of this photograph by W. Eugene Smith.
Called "Factory Reflected in River" and taken in 1955 it's just wonderful. There are thousands of pictures that use reflections to create the desired effect (and why not) but this has got to be my favourite. Everything about it is just right, the unusual framing (cutting off the tops of the furthest buildings), the contrasts, the way your eye is drawn around it. To me it's as if someone has started a painting on canvas and the paint has slowly dripped down across the frame.