Shahriar S. Afshar claims to have performed an experiment which contradicts Bohr's Principle of Complementarity, that is: light behaves as a either a wave or a particle depending on what sort of experimental apparatus you have — it is impossible to do an experiment which observes wave and particle properties of light simultaneously. I was taught that Complementarity was the bedrock of Quantum Mechanics, which is, as we all know, "the most well tested and successful theory in the history of physics".
Except it is apparently quite possible to perform such an experiment, and Afshar has done it.
Great edifices of philosophy have been built based on Complementarity and Bohr's Copenhagen Interpretation. My father must have been very impressed by Bohr's arguments, because he described these ideas to me when I was very young*, I suppose to impress upon me how mind-expanding science could be.
My favorite suggestion on how to adapt to the new result is to agree that there's no such thing as a Photon.
There was a brief discussion of the experiment and what it may mean on the July 30th episode of NPR's Science Friday. The July 24th issue of New Scientist magazine had a cover story on the topic, but registration is required to read it.
[*] "Light is both made up of things that are like rocks and is like the ripples a rock makes when you throw it in the lake — how could light be like both of those?", he'd say.