A Frank
Frank (adjective): Honest or direct; Without euphemism. (noun): A man who possesses tremendous variety of obscure knowledge or skill but does not display them frequently, thereby continuously surprising even close friends with his abilities.
Frank is the only one who tells it like it is. He doesn’t waste time with lies.
He knows everything but never shows off. He’s like a walking encyclopedia.
Frank is the only one who can fix the printer and knows the history of the office.