Jack O'Connor certainly cost me the most money, imparting his love of finely stocked rifles.
As for actual hunting, my recently departed elk hunting mentor.
I'll second Jack O'Conner and add Ernest Hemingway, Bob Foulkrod, Craig Boddington, Jim Shockey and the greatest wing shooter I every knew my grandfather.
I watch him nock down 26 one day with only twenty five shots from his Belgian Browning patented Remington. He was eighty and about six months post knee replacement. It was the last hunt we went on together. I was in my early twenties, home from college. The year was 1992. Most of everything I know I learned for him and my other grandfather, who were both avid hunters and fisherman. Both men served in WW II. The later was wounded at Iwojima and hung in a palm tree for three days while the Japanese marched underneath. I remember seeing the scares from the bullet holes, three in the front just below his heart and three coming out the back on either side of his spine. He liked to hunt hogs with a few good dogs and a knife.
The most important lessons may have been learned in the woods together but had little to do with hunting. It was about placing God first in your life, being a person of integrity and honor, learning to live with in your means, providing for your family, treating people, even those you don't agree with, with respect, loving those God has placed in your care unconditionally, lessons about life and what manhood and sacrifice really look like. They don't make them like that anymore!
There is a lot to be said about taking your kids and grandkids afield. Many of life's great lessons can be taught accompanied by a good dog and a nice over and under or in a deer stand with a good rifle.
This world needs a lot more influencers like that!