  Searching for two-body resonance decays is a central component of the high
energy physics energy frontier research program. While many of the
possibilities are covered when the two bodies are Standard Model (SM)
particles, there are still significant gaps. If one or both of the bodies are
themselves non-SM particles, there is very little coverage from existing
searches. We review the status of two-body searches and motivate the need to
search for the missing combinations. It is likely that the search program of
the future will be able to cover all possibilities with a combination of
dedicated and model agnostic search approaches.
