  The Peccei-Quinn anomalous global U(1)_{PQ} symmetry is important not only
for solving the strong CP problem with a cosmologically relevant axion, but it
may also be the origin of a residual Z_2 symmetry. This new symmetry may be
responsible for a second component of dark matter composed of an absolutely
stable Weakly Interacting Massive Particle, as well as for generating radiative
neutrino mass. Two specific realizations of this idea are proposed. In these
scenarios, dark matter detection is guaranteed at existing direct detection
experiments or axion searches. Observable signals at the Large Hadron Collider
are discussed.
