Depends on the kind of writing. If I'm doing an article, and I've gotten through transcribing and am actually putting my own words in and approaching the finish line, it can range from the humvee chase from THE ROCK to action cues from THE PRISONER, and occasionally THE ECSTASY OF GOLD from Leone, looped over and over. If I'm way behind schedule, it is usually time for Taiko drums, so I have incentive to finish before my head explodes from repetition.
If it is actual creative writing, then Goldsmith cues from all sorts of pics always inspire me. Not necessarily from the best movies, either. Music from Bronson's BREAKOUT and BREAKHART PASS, from Hill's EXTREME PREJUDICE, from FINAL CONFLICT or RIO CONCHOS ... Barry's Bond work, esp the early stuff like GIRL FIGHT from FRWL, gives me good visuals (that piece always makes me think of two space craft jockeying for position and shooting it out while falling out of orbit together.)
Not to slight Sol Kaplan and Fred Steiner, cuz stuff like the former's STAR TREK's DOOMSDAY MACHINE score has been a compelling force (for exercise and writing) my whole life. Ditto for the Sam Spence tunes done for NFL FILMS' various productions, which I personally would have recycled for a particular film if I had the chance.
For writer's block I go more eclectic ... could be Michael Small's anthem from THE PARALLAX VIEW (also heard before Schneider gets knifed in MARATHON MAN) , the piano duet from ROAD TO PERDITION, or Vangelis from THE BOUNTY. IF that doesn't work, then it is time for something drastic and old-fashioned sweeping, like the theme to SWASHBUCKLER or the sailing ship vs. ironclad sequence in NATE & HAYES.
If I'm having to write a deeply emotional scene, I usually have to have something with a voice in it playing, anywhere between Loreena McKennitt and late 60s Sinatra. Otherwise I'm pretty much an instrumental music guy, save for 70s rock (most of which I like for the long instrumental openings.)
The preceding are general approaches, since I try not to ritualize the use of music for powering my creative juices. I'll just drop a CD in at random some of the time, not knowing if I'm going to hear the BeeGees do YOU SHOULD BE DANCING or Elmer Bernstein's theme to THE SHOOTIST (which helped me come up with an opening of a spaceship flyby where you only see it in silhouette, then as it rolls over into sunlight while opening its cargo bay doors, the music surges and you see the word SASQUATCH lettered on the hull.)
I might not respond to music the same way most people do either ... it was pointed out to me in my teens that I tap my foot to the melody, not to the rhythm, so it might be I process all this stuff ass-backwards.