In the movie Blade Runner, is Deckard a replicant?

There is considerable evidence that Deckard is not a replicant.

Deckard is thrown about like a rag doll by every replicant he scuffles with—with the possible exception of Rachael,1 who doesn't try very hard. His ass is kicked even by Pris, who was described as a “basic pleasure model.” If you were assigning a replicant to blade runner duty, you would probably pick one whose physical capacities were at least equal to those of a basic pleasure model.

Deckard believes that he has quit the police force. He doesn't like his bosses or coworkers, he has to be threatened into returning to work, and he is insubordinate to the point of allowing Rachael to escape. If you were programming a replicant for blade runner duty, you would probably make him more enthusiastic about his work.

The memory-implant technology is new, but Bryant refers to Deckard as the “old blade runner” and acts as if they have worked together for a long time. Granted, this could be an elaborate lie (although why concoct a rocky relationship, see above) but at least it shows that if Deckard is a replicant, then the police know about it and are lying about it. The same police are sufficiently paranoid about replicants that they want to whack even the inoffensive Rachael as soon as Tyrell reports her missing. This does not jibe too well with them letting a new and experimental replicant roam Los Angeles with a badge and a gun.

The coincidence of the unicorn dream and the origami unicorn is not exactly the same as Deckard showing off his knowledge of Rachael's childhood memories. A recent dream is not the same as a childhood memory, and a unicorn is a single ambiguous symbol, not a detailed story like the two that Deckard tells Rachael. In other words, it could just be a coincidence, or show that Deckard and Gaff have similar taste in symbols. Gaff's origami chicken meant, “You're acting like a chicken,” not, “You dreamed about a chicken last night.” The unicorn could mean something like, “You're chasing an impossible goal,” not, “You dreamed about a unicorn and I know about it.”

Gaff does not say to Deckard, “It's too bad neither you nor she will live, but then again who does?”

In short, it's amazing how easily people are taken in when a lying Ridley Scott replicant gives a few interviews. Come to think of it, have those interviewers passed a V-K test lately?

1If Rachael has no built-in expiration date, as stated in the original cut, that would be consistent with her apparent lack of superhuman strength. After all, the light which burns half as bright burns twice as long.