I heard American Girl by Tom Petty and the Heartbreakers today and I got the idea for this thread, since that is one for me, given that hearing always makes me think of both Fast Time at Ridgemont High and The Silence of the Lambs.
I saw Fast Times in a theater and probably one other time, and it's probably been 30+ years. Haven't seen Silence in ages either. Probably should put on the re-watch list.
Ride of the Valkyries.
And the O Fortuna section of Carmina Burana
"For What It's Worth" by the Buffalo Springfield is sort of a go-to Vietnam/Vietnam-era song.
Which is funny because the song has nothing to do with the Vietnam War. Stephen Stills wrote it about a series of "hippie riots" in Hollywood in 1966. The song is also often linked to the Kent State shootings in 1970, which is obviously absurd since the song was released four years before that event.
Day-O and The Banana Boat Song have been in tons of movies, although the only one that comes to mind is Beetlejuice.