The needle drop refers to the moment when a licensed song is played in media.
My personal favorite has to be "Sunshine of Your Love" in Goodfellas. To me that is cinematic perfection. The sudden, loud burst of the guitar riff as we slowly dolly zoom in on De Niro, his eyes like a hungry wolf, the mischievous smile that momentarily flicks across his face as we, the audience, are told without a single word exactly what Jimmy is thinking - "Fuck it, I'll just kill everybody." It's just perfect.
What are some of your favorite moments like this? It can be any mood or tone - triumphant, sad, funny - just any moment where the perfect song is played at the exact perfect moment.