scammer

double-crosser, double-dealer

bluffer, charlatan, fake, faker, humbug, impostor (or imposter), mountebank, phony (also phoney), pretender, quack, ringer, sham

adventurer, fox, knave, prankster, rascal, rogue

slicker, smoothy (or smoothie), wheeler-dealer

plotter, schemer, sneak, sneaker