The 2014 Mad Hat award unanimously goes to Andy Read, Steve Sembay, Jenny Carter, Emile Schyns, and, posthumously, to George Fraser, for the paper Potential solar axion signatures in X-ray observations with the XMM–Newton observatory. Although the original arXiv paper sadly went unnoticed, this remarkable work was publicized several months later by the Royal Astronomical Society press release and by the article in Guardian.
The crucial point in this kind of endeavor is to choose an observable that is noisy enough to easily accommodate a new physics signal. In this particular case the observable is x-ray emission from Earth's magnetosphere, which could include a component from axion dark matter emitted from the Sun and converting to photons. A naive axion hunter might expect the conversion signal should be observed by looking at the sun (that is the photon inherits the momentum of the incoming axion), something that XMM cannot do due to technical constraints. The authors thoroughly address this point in a sentence in Introduction, concluding that it would be nice if the x-rays could scatter afterwards at the right angle. Then the signal that is searched for is an annual modulation of the x-ray emission, as the magnetic field strength in XMM's field of view is on average larger in summer than in winter. A seasonal dependence of the x-ray flux is indeed observed, for which axion dark matter is clearly the most plausible explanation.
Congratulations to all involved. Nominations for the 2015 Mad Hat award are open as of today ;) Happy New Year everyone!