  Weakly interacting massive particles (WIMPs) remain a prime candidate for the
cosmological dark matter (DM), even in the absence of current collider signals
that would unambiguously point to new physics below the TeV scale. The
self-annihilation of these particles in astronomical targets may leave
observable imprints in cosmic rays of various kinds. In this review, we focus
on gamma rays which we argue to play a pronounced role among the various
possible messengers. We discuss the most promising spectral and spatial
signatures to look for, give an update on the current state of gamma-ray
searches for DM and an outlook concerning future prospects. We also assess in
some detail the implications of a potential signal identification for particle
DM models as well as for our understanding of structure formation. Special
emphasis is put on the possible evidence for a 130 GeV line-like signal that
was recently identified in the data of the Fermi gamma-ray space telescope.
