The list is pretty simple--I'll list the composer's last name, and then the name of the piece(s). I've tried to include the "official" name as well as the name that most people know it by. Note also that this list is in no order whatsoever.
Some of you might not know these pieces by title, but believe me, you'll know them if you hear them. If you're really stumped, ask below.
(Some of these titles also require umlauts. I have no idea how to do them, so don't even ask. If you miss them, feel free to take a pen and add them as appropriate to your screen.)
Symphony No. 9 in D-minor, Op. 125
Symphony No. 5 in C-minor, Op. 67
Bagatelle in A-minor / "Fur Elise"
Hungarian Rhapsody No. 2 in C-sharp minor (Think "duelling pianos")
Walkurenritt / Ride of the Valkyries, from Die Walkure ("Kill the wabbit, kill the wabbit...")
1812 Overture, Op. 49 (Of course any piece of music that uses artillery as a percussion section is going to attract notice)
Toccata & Fugue in D-minor (Think "mad scientist's castle")
An der schonen blauen Donau / The Blue Danube Waltz, Op. 314
Also sprach Zarathustra, Op. 30 (Think 2001)
"Hallelujah" from Messiah, Op. 56
"Overture" from William Tell
The Barber of Seville ("Figaro, Figaro, Figaro...")
"O Fortuna" from Carmina Burana
"Hoe-Down" from Rodeo ("Beef. It's what's for dinner.")
Fanfare for the Common Man
"La Primavera" from The Four Seasons
Canon in D-major (Anyone old enough to remember those old Gallo commercials?)
Here is also a second list, composed of pieces that are pretty famous (from getting used in movies, commercials, and the like), but that people may or may not know.
"Dies Irae" from Requiem (Opening scene of The Shining)
"Mars, the Bringer of War" from The Planets (Trailer for X2)
"Nessun Dorma" from Turandot
"Vesti La Giubba" from Pagliacci (Most any gangster film where someone's getting whacked)
Adagio for Strings, Op. 11 / Agnus Dei (The scene in Platoon where Willem Defoe bites it)
"In the Hall of the Mountain King" from Peer Gynt
"On the Trail" from Grand Canyon Suite
Peter and the Wolf
Night on Bald Mountain
Anything you feel that should've been included or left out? Let me know below.