  We propose two complementary design principles for engineering
three-dimensional (3D) Weyl semimetals and superconductors in a layer-by-layer
setup which includes even and odd parity orbitals in alternating layers -
dubbed orbital selective superlattice. Such structure breaks mirror symmetry
along the superlattice growth axis which, with the help of either a basal plane
spin-orbit coupling or a spinless p+ip superconductivity, stabilizes a 3D Dirac
node. To explore this idea, we develop a 3D generalization of Haldane model and
a Bogoliubov-de-Gennes (BdG) Hamiltonian for the two cases, respectively, and
show that a tunable single or multiple Weyl nodes with linear dispersion in all
spatial directions can be engineered desirably in a widespread parameter space.
We also demonstrate that a single helical Weyl band can be created at the
$\Gamma$-point at the Fermi level in the superconducting case via gapping out
either of the orbital state by violating its particle-hole symmetry but not any
other symmetries. Finally, implications of our results for the realization of
anomalous Hall effect and Majorana bound state are discussed.
