talisman:

is an expression used to describe a person who is able to clearly and effectively express themselves, or who has a clever way with words. The connotation associated with accusing a person of having a “silver tongue” is, in itself, ambiguous. While at once it is admission of sophistication, it is in some cases an accusation of deceptiveness. Regardless of the connotation, the expression denotes a definite ability to effectively convince with rhetoric.

(Source: cougarchild)