Merriam-Webster's Word of the Day for September 25, 2008 is:

consigliere • \kohn-sil-YEH-reh\  • noun
: counselor, adviser

Example sentence:
After years of being a consigliere to the CEOs of Silicon Valley's top giants, Norman has decided to break out and head his own high-tech enterprise.

Did you know?
If you're a fan of The Godfather series of movies, the character Tom Hagen may have already come to mind. Hagen, the Corleones' family lawyer, was famously dismissed by the Don's successor and son Michael Corleone because he was not a "wartime consigliere." The word "consigliere" comes from Italian and has been a part our language since 1615; it was originally used of someone who served on a council in Italy. Currently, it is most commonly used to designate advisers to the Mafia -- a use that first appeared in English in a document from a 1963 session of the U.S. Senate. It is also often used generally of a political or financial adviser, or any other trusted adviser for that matter.