If you're a list-maker, sometimes it's fun to give yourself limitations, such as allowing only one film per director or only movies with vampires in them. Making a list of debut films is tougher because it's sometimes hard to know when to start. (Do you count short films as debut films? What if, as in the cases of Kathryn Bigelow and Federico Fellini, the first credit is a shared one?) Some of the greatest filmmakers made really unremarkable debuts: can anyone name, or has anyone actually seen, John Ford's debut? And David Cronenberg's official debut is a deadly dull film he made at college. Then there's the sticky question as to how valuable a debut film really is if the filmmaker did not live up to his or her promise (Justin Lin, etc.)? Not to mention that this kind of list requires actual research. I don't think you can plug "debut film" as a keyword into the IMDB search engine. You have to actually comb through your DVD collection and lists of your favorite directors to find the great debuts.