My Aunt once told me a story that involved some manner of con artist or sheikster or ne'er-do-well.
(That reminds me, a friend (a reticent, gregarious, oft-narcotized, Sun Ra loving film student with a good heart) recently told me about moving around a lot as a child and I asked him, 'Was your dad in the army or some kind of traveling work?' 'No. Ne'er-do-well,' he responded.)
Anyway, my aunt, with a Boston inflected, schoolteacher & self-cultivated-King's-English accent, called this dubious man in her anecdote a 'flim flam man.' (pronounced: Flee-im flaahm maahn. The 'aah' is pronounced by opening your mouth, pulling up the corners as if to smile and issuing the 'e' sound in 'bed.')
Sooo... Let's have this list be about two things:
1) Synonyms for confidence men, mountebanks, sheisters and the like.
2) silly, fluffy, fly-wheel, flighty, flyaway, light and baby-talkish sounding synonyms for other, perfectly sharp and adult words. Of course, this latter catagory will be much more subjective and we shall have to fall back on that old and most unreliable modality of communal order: the honor code. Bonus points if your word is not slang & the synonym &/or referent of your featherweight word is particularly sharp, rough, sinister or stern. egs.... hm...can't think of any at the moment.....