Wow, I have to agree with Evan and the others. If you were to go back 10-20 years ago you would not have even heard of the majority of those on the list. Yes, they have made a contribution, but they aren't pioneers.
I would like to add 3 people to the ongoing list; Roger Conant, Bill Haast, and Don Hamper.
My vote would go to Carl Kauffeld for his book Snakes: The Keeper and the Kept