  Initial- and final-state rescattering, neglected in the parton model, have a
profound effect in QCD hard-scattering reactions, predicting single-spin
asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic
reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and
nuclear shadowing and non-universal antishadowing--leading-twist physics not
incorporated in the light-front wavefunctions of the target computed in
isolation. I also discuss the use of diffraction to materialize the Fock states
of a hadronic projectile and test QCD color transparency, and anomalous heavy
quark effects. The presence of direct higher-twist processes where a proton is
produced in the hard subprocess can explain the large proton-to-pion ratio seen
in high centrality heavy ion collisions. I emphasize the importance of
distinguishing between static observables such as the probability distributions
computed from the square of the light-front wavefunctions versus dynamical
observables which include the effects of rescattering.
