I mean, the first 'Back to the Future' is kind of a perfect script, I think, in terms of handling time travel the best. It depends on your definition. To me, that means it effectively uses it in the story.
I would say that the Pentagon Papers case of 1971 - in which the government tried to block the The New York Times and The Washington Post that they obtained from a secret study of how we got involved in the war in Vietnam - that is probably the most important case.