  We investigate a class of gravitational pp-waves which represent the exterior
vacuum field of spinning particles moving with the speed of light. Such exact
spacetimes are described by the original Brinkmann form of the pp-wave metric
including the often neglected off-diagonal terms. We put emphasis on a clear
physical and geometrical interpretation of these off-diagonal metric
components. We explicitly analyze several new properties of these spacetimes
associated with the spinning character of the source, such as rotational
dragging of frames, geodesic deviation, impulsive limits and the corresponding
behavior of geodesics.
