The Imperial March from Empire Strikes Back or the Theme to Psycho I find it makes the experience much more cinematic. One of my All time favorite soundtracks is John Williams score to Jaws. Its perfect in every way, and not just the iconic two tone Da-dum, Da-dum that signals the presence of the shark, listen to Track Two, Chrissy's Attack.
The final few seconds when the music cuts out and it's just some dude whaling on an anvil thrill me. Pure genius John Williams, pure effing genius. Williams signed on for the second Jaws movie, affectionately titled Jaws 2. The movie was just awful (I kind of love it, as one of those childhood memories...I was a weird kid) but the score is still top notch.
Alan Parker took over for the third installment in the Jaws franchise. Easily one of the stupidest and most awesome movies ever made and it was in 3-D. It's also got the most amazing ending of any film ever!! Since words can't describe, just watch. It's like a giant turd with teeth.