Lady beetles are predators frequently sold for biological control, although their effectiveness is somewhat dubious.  The Asian Multi-Colored lady beetle was intentionally released in North America as a control agent for aphids (as seen here), but they rapidly became a pest in their own right.  The Harmonia introduction is a classic instance of biological control gone wrong.  The beetles congregate inside houses in the winter, biting the occupants, and they have driven a number of native, non-pesty lady beetles to local extinction.