  We propose a simple realization of the three-dimensional (3D) Weyl semimetal
phase, utilizing a multilayer structure, composed of identical thin films of a
magnetically-doped 3D topological insulator (TI), separated by
ordinary-insulator spacer layers. We show that the phase diagram of this system
contains a Weyl semimetal phase of the simplest possible kind, with only two
Dirac nodes of opposite chirality, separated in momentum space, in its
bandstructure. This particular type of Weyl semimetal has a finite anomalous
Hall conductivity, chiral edge states, and occurs as an intermediate phase
between an ordinary insulator and a 3D quantum anomalous Hall insulator with a
quantized Hall conductivity, equal to $e^2/h$ per TI layer. We find that the
Weyl semimetal has a nonzero DC conductivity at zero temperature and is thus an
unusual metallic phase, characterized by a finite anomalous Hall conductivity
and topologically-protected edge states.
