[devinj]

"Fountain", by Marcel Duchamp. You might argue that Duchamp was an experienced professional at art in general (being 30 and the producer of less-famous works), but it's a urinal that he purchased in a store and signed.

It's also one of the most influential art pieces of the 20th century. It, and his "found art" movement in general, are the cornerstones of the redefinition of art and mark the invention of conceptual art. Art no longer has to do with who made it, or how, or how much effort was put in. It's about intent. If you buy a pencil and say it's art, it's art (if perhaps not very good art).

[ZeroGravitas]

Apparently Duchamp actually went to great lengths to create or to modify the items he "found", and then denied changing them at all, in what is perhaps yet another level of irony. Or so I've read.

http://en.wikipedia.org/wiki/Readymades_of_Marcel_Duchamp#Do...