Reginald VelJohnson played the jail guard who came to the Ghostbusters rescue, informing them that the Mayor wanted to speak to them after they had been thrown in jail, in a fairly low-key cameo. He also played Sgt. Al Powell in the first two Die Hard movies - a role he later reprised in the NBC series Chuck. Evidently VelJohnson must have an authoritative face, because those are the kinds of roles he tends to get in general.