Examples off the top of my head:
John Cage "composed" a song consisting of just silence.
Marcel Duchamp exhibited a urinal which he simply purchased from a store.
Yves Klein exhibited 11 paintings that were exactly the same. They were simply blue, no structures or subject. But he priced them all differently.
I can't remember the name, but I recently read about a photographer who exhibited nothing and then made photos of confused faces during the exhibition.
I can't remember which art prize it was, but there once was an art price which asked artists to "make a piece of art that represents your country". And a female artist wrote back "Dear jury, just give me the art prize for my reputation. You can keep the money in return. This would also represent my country as we have so much corruption here". And she won.