A penny dropped from the Empire State Building would not kill someone standing below, most likely. The observation deck is 1050 feet high, and the penny would reach a maximum velocity of 57 miles an hour after falling 500 feet. That’s enough to hurt pretty bad, but only a very very lucky (unlucky) shot would kill you. Most importantly of all, there is an updraft. Tossed coins generally land on the setback roof of floor 80.
The calculations come from the February issue of Popular Science, the article itself is not available on-line.