2 Val Lewton (89.38/8) A tough call that seems to go against the spirit of the thread. He seldom took credit for writing the films he produced but it's generally agreed his was the guiding hand in their scripts, and occasionally direction, always uncredited. Another user (not me) has gone through and added him as a writer on all of them, or at least the famous ones
3 George Toles (89.00/5) Once-frequent co-writer of Guy Maddin's
4 Philip Yordan (88.33/12) Contributor to some of the most distinctive and unusual films of the classic Hollywood era: Johnny Guitar, The Chase (1946), Day of the Outlaw, God's Little Acre, The Black Book, and many more, seven in toto with Anthony Mann
5 Borden Chase (88.13/8) Mann's other favourite screenwriter, four films. Also wrote great westerns for Hawks, Vidor, and John Sturges
6 Barry Wong (86.00/5) Scenarist for Sammo Hung and other HK action maestros
7 Waldemar Young (86.00/5) Another Old Hollywood goon, pretty diverse body of work including multiple films with Lubitsch and Tod Browning
8 Tsutomu Tamura (85.00/7) Regular collaborator with Nagisa Oshima and Yoshishige Yoshida
9 Ernesto Gastaldi (85.00/5) Giallo, mostly. Did eventually dabble in directing, with 4 or 5 now-very-obscure films.
10 Nicholas St. John (83.89/9) Only films were with Abel Ferrara, whom he befriended in high school. This a man who seen some shit. Left the business in the 90s. From a Ferrara interview earlier this year:
Right after that are two more writers identified strongly with one director: Ennio Flaiano (Fellini) and Bill Richmond (Jerry Lewis), a run that's probably a more apt portrait of my taste than I would care to admitHe was a deep, deep Christian, didn’t drink, didn’t do drugs. But when we started making money in the 1980s, I started spinning out of control. It got even worse in the 1990s, when we were in L.A. Meanwhile, he’s married and living in his mother’s house. We were making bread, we were making movies, and then he just said basta, man. No more. He walked away when he was the height of his earning power, but I mean, it was never about money for him. It was never really about money for me, either. But this business just had nothing to offer him. Its a dangerous game, man.