[Nosferatu@Cult Labs]

This video explains the reasons why Deckard could be/is a replicant very well.



I personally think he is one because of the unicorn and Gaff's line "It's a shame she won't live – but then again, who does?" This is the second time the line has been heard, but the second time reinforces (to the audience) Deckard's realisation that he, like Rachel, is a replicant with implanted memories.