Coexist

Picture is courtesy of "marcusg" who published it on Flickr with the collowing caption:

[U2 lead singer] Bono said this was grafitti he saw... calls to peace between the religions, Islam is represented by the cresent moon, star of david for the Jews and Christian cross.

To me it looks like a modern version of the three rhombs idea that is discussed at length in Asher Eder's book THE STAR OF DAVID. 

Bono referred to this symbol as he sang, “Jesus, Jew, Muhammad, it’s true…All sons of Abraham. Father Abraham, speak to your sons. Tell them, No more!”
Bono first saw the “Coexist” symbol painted as grafitti on a wall in Chicago.

Coexist is actually the work of Piotr Mlodozeniec, a Polish graphic designer living in Warsaw. He created the CoeXisT image in 2001 for a contest hosted by The Museum on the Seam for Dialogue, Understanding and Coexistence in Jerusalem.