Dissimulation. It's an unusal word, but I think it's the only word that exactly describes the narcissist's tactic to con people. He or she dis-simulates their true self. They act like the antithesis of what they are.
At Sanctuary for the Abused, we get an example of what I mean in the child molester:
Some tell people they think child molesters should be shot, while others work very hard to present themselves as a concerned citizen and pillar of the community.
Which reminds me of a wise man (Jesus of Nazareth) who said that people who perform good works to be seen doing them deserve no credit for them.
Why do child molesters do this? To Block the Kick in case any child tells on them.
How better to dissmulate a child molester than to make sure everyone hears you expressing outrage about "those people" who molest children? Better yet, put it on thick by becoming an activist against child abuse in your community. Yell a lot about how you think child molesters should be shot.
Laughing up your sleeve the whole time.
Indeed, what better disguise is there for a child molester than the habit of a priest who gets to be called "father"?
Dissimulation. It isn't brilliant: a six-year-old is smart enough to think of and play this trick. It's just so low that it comes in under most people's radar.
I give another example of dissimulation in this account of the narcissist who put on an extravangant show of love for her dying mother -- only to show her true colors when nobody was around to see how she treated her dying mother.