Abstract: It has been shown that the energy distribution of the massless decay product from the 2-body decay of a scalar or unpolarized mother particle has a peak, whose location is identical to the fixed energy of that particle in the rest frame of the corresponding mother particle although its underlying boost distribution is unknown. In this talk, I will discuss how this observation can be applied to anomalous excesses in cosmic ray measurements, having dark matter interpretation in mind, together with several concrete examples such as the Galactic Center GeV excess, line-like gamma-ray excesses, and MeV-range gamma-ray signatures under the dynamical dark matter framework. I will also briefly discuss distinctive morphological features of the relevant cosmic ray energy spectra, which can used for unveiling the details of underlying dark matter scenarios.