Very first I can remember were -
Mentzer -

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It was that shot or one close to it. He just looked rugged and masculine, and not cartoonish.
Kazmaier -

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There have been others Rigert, Barmanski, Patera, Doug Young, etc.... But those have to be the first. Also Hulk Hogan should get a spot in there, simply because he sort of planted the lifting bug in my mind as a little kid, although it would be a decade plus later before I started lifting semi seriously.