In this talk I will do three things. First, I will outline the conditions under which the interaction rate of inelastic processes with a system consisting of N targets scales as N^2. Second, I will present computations of interaction rates for several weakly interacting particles, including the Cosmic Neutrino Background and QCD axion dark matter, and will explain the underlying physics. Third, I will introduce new quantum observables that do not rely on net energy transfer, but can still extract these N^2 effects. This talk will not address a concrete experimental proposal, but the effects presented may point to a new class of table-top and ultra-low threshold particle detectors.