I am always amazed at how few people have seen Chungking Express, despite it being one of the most popular hong kong films ever made--such a delightfully powerful film. Eternal Sunshine of the Spotless Mind is another that few have sadly seen. For something a little darker you might want to check out Coppola's powerhouse one-two punch of The Conversation and Apocalypse Now (theatrical version), films far more powerful and entertaining than that silly mafia soap opera he is also known for. Also, if you are in the mood for something animated The Iron Giant continues to be another ones of the unseen masterpieces. Really there is so much to recommend, it really boils down to mood and content. I try to refrain from overtly sad films if you are doing a marathon since it kind of leaves you feeling drained and unenergenic by the end. Also, seeing as Scorsese is all the rage now with his departed, you might want to check out the early 80's absurdist comedy-drama that saved him from the destruction that peers like Coppola, Friedkin and Lucas faced, his greatly undeerated After Hours.