Thought this photomontage by Banksy is very good. The photograph of the work was taken at his exhibition in Santa's Ghetto gallery in Central London.

The greatest exponent of photomontage was Helmut Herzfelde. He was born in Berlin, Germany on 19th June, 1891. During the First World War Herzefelde began contributing work to Die Neue Jugend, an arts journal published by his brother, Wieland Herzfelde. He was drafted into the infantry where he meets George Grosz.

Herzefelde continued to contribute illustrations to Die Neue Jugend. While working for the journal Heartfield developed a new style of work that later became known as photomontage (the production of pictures by rearranging selected details of photographs to form a new and convincing unity). A pacifist, Herzfelde, changed his name to John Heartfield in 1916 in protest against German nationalism.

http://www.spartacus.schoolnet.co.uk/FWWheartfield.htm

It is difficult to know which one to pick but this one probably best explains the growth of fascism in Germany.

Millions Stand Behind Me, 16 October 1932