Don’t believe the hype about Beethoven’s Fifth and Ninth symphonies. His greatest is actually the Seventh. 
The sublime 1st movement alone is worth the price of admission, as they say.
You misspelled “2nd movement.”
Then I also misspelled “sublime” and should have written “haunting and serene.” 
Ones you may know via Allan Sherman:
Brahms’ “Hungarian Dance Number 5” = “Hungarian Goulash No 5”
Grieg’s “Norwegian Dance Number 2” = “I Can’t Dance”
Ponchielli’s “Dance of the Hours” = “Hello Muddah, Hello Fadduh”
Borodin, from Polovtsian Dances in his opera Prince Igor: Stranger in Paradise from the musical Kismet. Other numbers in the musical were also based on Borodin’s music. Kismet (musical) - Wikipedia
Rachmaninoff, Piano Concerto #2, 2nd movement, used in the bridge of All By Myself.
Not sure if its considered classical…but a bit more modern, Gershwin’s Rhapsody in Blue.
Certainly you’ve heard the 3rd movement of Chopin’s Funeral Sonata.
I love sharing this list of Standard Snippets – classical pieces everyone knows from films and movies, many of them so routinely used that it had just never occurred to me that someone wrote them at some point.
Many of the pieces in it have been named already in this thread, but you might enjoy seeing them compiled.
From Mozart’s Requiem - Lacrimosa It’s lovely and I hear it a lot.
The Flower Duet from Lakmé by Léo Delibes has been used in commercials and movies.
Check out Disney’s Fantasia and Fantasia 2000
How no one has mentioned the Fire Bird Suite yet is a travesty.
Here are some slightly lesser known but universally popular works.
I think this thread may also be missing Bach’s Cello Suites, anything from Verdi’s Il Trovatore, the entirety of Carmen and Nussun Dorma.
Nice link. I’ve been wondering what the ‘snobby rich people’ music was that they play on Adam Carolla’s podcast whenever he mentions something that pegs him to being pretty well off financially. I thought it was Vivaldi’s Spring, but I think it’s actually ***Minuet ***by Luigi Boccherini.
Is that site a wiki? IOW is it user editable? I’d like to suggest Gary Glitter’s Rock & Roll Part II as ‘generic sports anthem’ and James Horner’s Bishop’s Countdown as ‘ubiquitous climaxing movie trailer music’…
If you like the works of Alfred Hitchcock, you will have heard Charles Gounod’s Funeral March for a Marionette
The other piece which features heavily in that film is the [COLOR=“black”]Adagio in G minor[/COLOR], usually attributed to Baroque composer Tomaso Albinoni but actually written in 1958 by musicologist Remo Giazotto based on a small fragment by Albinoni.
I’d second Carmen, and If you’ve ever seen old reruns of Gilligan’s Island you’ve heard snippets (the episode where Phil Silvers guests as Harold Hecuba, film producer, uses cuts from Carmen as some of the background music for the Musical version of Hamlet the castaways put on. They also used parts of the opera Tales of Hoffman).
Wait, did anyone mention Samuel Barber’s Adagio for Strings yet?
Because that piece is all over the place.
ETA: See: Platoon.
Rather surprised that the "Largo al Factotum" from the Barber of Seville hasn’t been mentioned yet.
See post #4
Apologies–searched for the proper name. 