Poll: 70s Paranoid Thriller Films

In the 1970s, particularly in the shadow of Watergate and general disillusion with the government or corporate establishment, there was a particular genre of thrillers which became popular, that involved various shadowy conspiracies. These could involve the government (or secret rogue groups within the government), corporations, or other nebulous groups of powerful people behind the scenes. Often a lone person (or very small group of people) will see or notice something that puts him or her on the trail of such a conspiracy. This person could be an intrepid reporter, or a small-time cop or sheriff, or a private investigator. Often this person has no clue at first what he's getting himself into, but as his curiosity peels back more layers of the onion, he'll suddenly find a stray bullet whizzing by him, or some other grave threat to his health coming from the shadows. This will almost always stiffen his resolve to find out what's going on, and the race is on for him to gather enough evidence to expose the truth before his newfound foes end him. His success in that race isn't always guaranteed. Which of these "paranoid thrillers" of the 70s intrigued or frightened you the most? Discuss here