some on my hard drive:
Chinatown
Annie Hall
Gods and Monsters
The Sweet Hereafter
Chasing Amy
Good Will Hunting
Shakespeare in Love
Ghost World
Up in the Air
Your taste may vary. Also, read every one you can find various versions of, even if it's for some junkie movie like...I dunno, re1gn of f1re. I read several versions of American Beauty, not at all a favorite of mine but well written, which changed a whole lot over time.
FYI, I no longer write scripts; tried it, was too different for me and I reverted to fiction.