I'm not sure if I can pick a favorite. I have a lot. However, John Williams is a great composer. I love all his soundtracks (Indiana Jones, Star Wars saga, Jurassic Park) Another song I really like is Endless love from the movie The Myth. The piano version of this song is so touching that it brings me to tears. Check it out
My favorite song from a movie (at the moment) is Extreme Ways by Moby from the Bourne Identity movie, the freaking song is so catchy! Other then this, I can't find any other songs from movies that I like.
Zydrate Anatomy from Repo! The Genetic Opera is one catchy song...I recommend it for anyone interested in wanting to hear some good Rock Opera (the song)
I like too many to tell. Okay let's try: Once Upon A Time in the West, all the Star Wars, Harry Potter (everything by John Williams), Battlestar Galactica (original TV-Series), Willow, any film score by Ennio Morricone, Maurice Jarre, Vladimir Cosma (french comedies), Star Trek, Basil Polidopouris (Conan the Barbarian), music score from the Looney Tunes, Mission Impossible (original TV-Series), Lost in Space (original TV-Series), Soundtracks made by John Carpenter, and some composers from old movies as well. That's it for now. 85% of my music collection is composed of film scores and soundtracks so...