  Using gamma-ray data from observations of the Milky Way, Andromeda (M31), and
the cosmic background, we calculate conservative upper limits on the dark
matter self-annihilation cross section to a number of final states, over a wide
range of dark matter masses. We first constrain annihilation to a pair of
monoenergetic gamma rays, and show that in general our results are unchanged
for a broader annihilation spectrum, if at least a few gamma rays are produced
with energies within a factor of a few from the dark matter mass. We then place
constraints on the self-annihilation cross section to an electron-positron
pair, using gamma rays produced via internal bremsstrahlung radiative
corrections. We also place constraints on annihilation into the other charged
leptons. We make conservative assumptions about the astrophysical inputs, and
demonstrate how our derived bounds would be strengthened if stronger
assumptions about these inputs are adopted.
