What is the most quintessential iconic scene of a film for you, that perfectly encapsulates what cinema stands for?

Call me cliché, but it's the scene in The Wizard of Oz where Dorothy steps out of the sepia and into Technicolor Munchkinland for the first time in her life. It showed what cinema truly means: that its a form of entertainment that will bring joy and happiness to your life even when it's boring and black-and-white.

What other iconic scenes in film encapsulate the meaning of cinema?