  We propose a WIMP candidate with an ``excited state'' 1-2 MeV above the
ground state, which may be collisionally excited and de-excites by e+e- pair
emission. By converting its kinetic energy into pairs, such a particle could
produce a substantial fraction of the 511 keV line observed by INTEGRAL/SPI in
the inner Milky Way. Only a small fraction of the WIMPs have sufficient energy
to excite, and that fraction drops sharply with galactocentric radius,
naturally yielding a radial cutoff, as observed. Even if the scattering
probability in the inner kpc is << 1% per Hubble time, enough power is
available to produce the ~3x10^42 pairs per second observed in the Galactic
bulge. We specify the parameters of a pseudo-Dirac fermion designed to explain
the positron signal, and find that it annihilates chiefly to e+e- and freezes
out with the correct relic density. We discuss possible observational
consequences of this model.
