Has an NBA game ever ended 80-79?
It has. 80-79 has been a NBA final 24 times in 73,172 games. The first was Minneapolis Lakers beat Rochester Royals on March 27, 1949; the latest was New York Knicks beat Orlando Magic on April 11, 2015.
That makes 80-79 the 882nd most common final score out of 3,189 that have ever occurred in NBA. One point away, 81-79 has happened 27 times and 80-80 has happened never.