1. "Rosebud..." - Citizen Kane
"Rosebud," the dying word that spawned a legendary director, actor and film, Rosebud is perhaps the most important lone word in cinema history. Charles Foster Kane, newspaper tycoon based on William Randolph Hearst, is the star of Orson Welles' magnum opus Citizen Kane. Widely considered the greatest film ever made, this 1941 film traverses the life of a man from his humble beginnings to the aftermath of his lonely death. Rosebud, a symbol of Kane's lost youth and innocence, is the dying words on his lips. The film follows the investigation of a man trying to unravel Kane's life in order to determine the seemingly cryptic final word spoken by this powerful man. Ultimately, they decide that a lone word could never define a single person, but Citizen Kane shows that "rosebud" certainly comes close.
Honorable mentions: Fight Club, White Heat, Wizard of Oz. Did I miss others? Leave a comment or find how to get at me in my bio below.