There are many Great legendary photographers out there and they will all influence someone in different ways. for me it was Avedon and Leibovitz. I hope that one day I can do for someone what they have done to me.
If there are any aspiring commercial and portrait photographers out there I recommend you view the video "American Masters - Richard Avedon: Darkness and Light (1996)" and "Annie Leibovitz: Life Through a Lens (2008)".
I recommend these only as an inspiration for one to become their own artist, not to imitate. The rebirth of new ways of seeing the world is what makes life interesting. These are just two photographers that have influenced and helped me continue being who I am as an artist, but there are many and will be many more that will continue to influence me in my life as I hope to move people in their lives.
American Masters - Richard Avedon: Darkness and Light
Not to mention the bunch of books you can find on these two also.