Awesome / The Day the Earth Stood Still (1951)

• First thing Gort does when he thinks his master is in danger? Blow up a tank or two.
• When Klaatu and Billy visit Professor Barnhardt, they find the man isn't home. So, Klaatu cleverly makes an addition to a blackboard-covering equation before they leave. Needless to say, Bernhardt is notes he was rather impressed by this when he and Klaatu finally meet.
• Klaatu's "small" demonstration of power. Wherein he deliberately, though briefly shuts down all electrical power all around the globe in a full on 30-Second Blackout. He even goes to lengths to insure that things like hospitals and planes are not shut off, preventing any accidental deaths.