Too many to mention but some that come to mind
Stagecoach: Ringo telling Dallas about his ranch
The Birds:
The birds landing behind Tippi Hedren in the playground
Heat: The bank robbery shootout.
My Darling Clementine: Wyatt Earp and Clementine dancing at the church.
Johnny Guitar: Joan Crawford playing a piano when the posse arrive.
Singin' In the Rain: Gene Kelly singing the theme song.
La Dolce Vita: The children who've seen a miracle.
Apocalypse Now: The helicopter raid
Ferris Bueller's Day Off: At the art gallery.
Sunset Boulevard: Gloria Swanson's final scene.
My Little Chickadee: WC Fields telling the story about Chicago Molly
Could go on forever with this