Characters
Me? I'm dishonest, and a dishonest man you can always trust to be dishonest. Honestly. It's the honest ones you want to watch out for, because you can never predict when they're going to do something incredibly... stupid.
— Jack Sparrow • Pirates of the Caribbean: The Curse of the Black Pearl

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Jack turns an admission of dishonesty into a claim of reliability. Someone consistently untrustworthy can at least be anticipated, while an honest person may act unpredictably. The repeated insistence on honesty sharpens the joke, making a crooked argument sound like sensible advice about whom to trust.
Context reviewed