  The boosted Taub-NUT metric with zero ADM mass is shown to possess a dual
momentum in the direction of the boost giving credit to the existence of
another 4-vector K_\mu in linearized gravity associated to the NUT charge and
dual to the usual P_\mu. Taking the infinite boost limit we obtain a shock
pp-wave with NUT charge. We show that the latter is the gravitational dual of
the infinitely boosted Schwarzschild metric, also known as the Aichelburg-Sexl
pp-wave. We review the fact that this new shock pp-wave is also an half-BPS
solution of N=1 supergravity. It has a BPS bound equal to K_t=|K_z|.
