Captain Jack Harkness

A dashing former Time Agent working as a conman in Blitz-era London, Jack Harkness flirts his way through danger with a rakish grin and a sonic device or two of his own. He's charming, morally slippery, and entirely too pleased with himself — a rogue the Doctor and Rose can't quite trust yet can't resist.

Barrowman plays him with such unapologetic swagger that his introduction as a small-time crook barely registers before you're won over. The writing lets him be flirtatious with absolutely everyone regardless of gender, treating it as a matter of course rather than a statement, which made him feel genuinely new.