I would say dominant Fe, auxillary Si. Primarily using Fe to relate to people and using Si help with people reading by evaluating body languarge tone of voice, etc.
These would be the more adept ones, that can sell you stuff you don't really want and always have the men or women swooning over them.
The people that try to be smooth, but come off as creepy or obnoxious are probably people acting against type, using their shadow functions. Introverts trying to be extroverts or thinkers trying to be feelers in the hope that will make them more popular or get them dates.
I know an ESFP. And if I ever danced with the devil in the pale moonlight, it would be him. He's a friend and a mischievous rogue if I ever met one. He's in damn good need of a good influence (such as myself?)... He is truly just a friend. He is in a romantic relationship with someone else, as am I. Our contact is intermittent and strained by distance, because frankly (other than the fact that I am cyclically self-absorbed against my better notions of human virtue) --friend though he may be-- and --loyal that I certainly am-- I fear that he has the ability to charm the pants right off me if he set his mind to it and if I was in a fragile moment, or any woman of weaker constitution.
He is capable of an absolutely irresistible charm and I'll be damned if that sonofabitch doesn't know it. He's not even close to the best looking man I've ever met. But he doesn't have to be. He's got a smile that could melt polar ice caps and stop traffic. I suspect his extroversion isn't extreme, so there's just enough social reticence to be intriguing.
God save the girl he's laid his sights on. He's got the X-factor which can best be described as not the ability to fool people, because he sure as hell doesn't fool me, which is perhaps why we're such good friends --but because he has the ability to persuade/cajole against your better judgement. It's like the Cheshire Cat beckoning you into the bowels of the enchanted forest you both know is forbidden, but which he has managed to convince you to do anyway since you're together... and it would be rather exciting... and no one would have to know... and who will it harm?... *wink* *grin* You get the drift.
And I know better than to EVER tell him that. I'd be too afraid he'd be encouraged, enlightened, or empowered.
I've also played with fire enough times to learn not to. Who says we aren't capable of learning?
There may be other equally suave types out there, but he is one of the few people I've met that is capable of charming me. Perhaps it is just the chemistry of our two types tapping into one another's desire for escapadal adventure. I'm not exactly sure. But I do know I've seen him at work in social spheres with an ISTJ, an ExFP, and an ESTJ and he seems to have had the same effect.
"There is no god; there is only us. Savage and fragile."