[Zero]

no contest - psycho. hitchcock's little gimmick of 'not allowing anyone into the film after it started' literally changed the way we see films. prior to this period, films were run on a continuous loop with A and B pictures separated by shorts and news reels. people could and would walk in at any point and simply watch the rotation all the way around. hitchcock's gimmick proved that people were willing to stand in line and enter a theater at a specific time.

as for most controversial - a different question - NOLD was pretty controversial. probably, in a technical sense, Natural Born Killers (if you see that as horror) is the most controversial as it has been wrapped up in the most extended legal wranglings over supposed copy-cat cases.