Harry Julian Fink's episodes
The episodes he wrote for Have Gun-Will Travel are so dark and complex it's amazing. I've gotten to where I can recognize his stamp even before seeing his name in the credits. He always left a less than tidy resolution that added realism to the show.
I just finished watching Fink's season 4 episode The Killing of Jesse May last night. It was chilling when Robert Blake's character starts that whistling at the end. A few days before that I watched A Head of Hair. Amazing, amazing writing.