Having seen all the films that Charlie Chaplin has directed, I suppose it's no surprise that he's also my most-seen writer, too, given the amount of control and involvement Chaplin had in his films.
The next three names in the list--Maltese, Foster, and Pierce--all wrote a bunch of Looney Tunes shorts.
Ben Hecht, next on the list, has a fascinating filmography, writing superb films like Notorious, Spellbound, Scarface, Design for Living, Stagecoach, The Thing, and Strangers on a Train, but also z-grade stuff like Queen of Outer Space, the 1967 version of Casino Royale, and Switching Channels.
Felix Adler wrote Three Stooges shorts.
Ian Fleming makes the list thanks to James Bond and Chitty-Chitty-Bang-Bang.
David Lynch, of course, writes or co-writes most of the material he directs.
Clyde Bruckman is another writer of Three Stooges shorts, but also features from comedy greats such as Buster Keaton and Harold Lloyd.
Woody Allen, like Chaplin and Lynch, writes much of his own material.
Stephen King makes the list, I suspect, because of "story by..." credits for the many adaptations of his novels and short stories.
Laurent Bouzereau produces short documentary "making-of" subjects that appear as special features on many of my discs.
Orson Welles, again, is another film polymath.
George Lucas makes the list thanks to Star Wars, Indiana Jones, American Graffiti, etc.
Sylvester Stallone, I suspect, is here thanks to the Rocky and Rambo franchises.
Elwood Ullman is another Three Stooges writer. What a fun job that would have been...
Richard Matheson is a well-regarded prose fantasist, SF author, and contributor of teleplays to The Twilight Zone, among other shows. Here for adaptations, much like King, I suspect.
Ethan Coen is of course one-half of the famous Coen Brothers writing-directing team.
And finally, David Cronenberg is another director who writes much of his own material.