  We present a 1-loop perturbative calculation of the fermion propagator, up to
O(a^2) (a: lattice spacing). The fermions are described by Wilson, clover and
twisted-mass actions; for gluons we use Symanzik improved actions (Plaquette,
Tree-level Symanzik, Iwasaki, TILW, DBW2). Our results are given in a general
covariant gauge, and their dependence on the coupling constant, the external
momentum, the masses and the clover parameter is shown explicitly. We also
study the O(a^2) corrections to matrix elements of unpolarized/polarized
fermion bilinear operators, which include up to one derivative. These
corrections are essential ingredients for improving, to O(a^2), the
renormalization constants of the operators under study. In addition, they can
be used to minimize lattice artifacts in non-perturbative studies.
