The fictitious kind. Deckard was human. : )
Philip K. Dick himself, Hampton Fancher (the screen writer), Harrison Ford (Deckard), and the producers of the film (the people that hire the director) all state clearly, and consistently, that Deckard was human. They have stated that from the beginning of production on through to this very day. Think about that for a moment and let it sink in.
To say he is NOT human undermines much of the movie when you think about it. As nifty an idea as it is, the notion detracts much more than it adds. But the argument has been around since the beginning. Harrison Ford actively argued against it at one point during shooting and stormed off. Ford has stated clearly his red-eye scene was a mistake, and that on set the effect was intended solely for Rachel.
Ridley is the revisionist, by adding the unicorn after the theatrical release (he admits the footage was shot for a different movie entirely) and stating blithely in his 2007 Final Cut special features (twice) that Deckard was a replicant – 25 years AFTER THE FACT! He thus backed away from his long standing, ~“There is no correct answer to that”, or, ~“To answer that misses the point.”, etc., which supports the notion of an intentionally polysemous art.
All things considered, it seems to me that to flatly insist: “Yes, Deckard was a replicant”, is the worst of all possible answers.
To my mind Scott's use of a unicorn [spliced in, after the fact] says much more about his sublime trolling skills to spur confusion and debate than it does proving Deckard a replicant.
Besides, I hear Leni Riefenstahl prepared a director's cut of Triumph of the Will before she died. In the special features she will explain the newly introduced shot of her behind a camera filming, where her feet are in shackles.