When I first became a Christian, i.e. joined a Christian fellowship, I chose membership in the Seventh-day Adventist Church. After immersing myself in their doctrines and commentaries, and the writings of their false prophet Ellen White, I finally came to the realization that I was in a cult, a dangerous cult.
After leaving the Adventist church, I remained dubious of man's commentaries on the word of God, and I resolved to allow God to teach me through His Holy Spirit sans commentaries and fellowship. I praise God that I grew in understanding of His word, and can say without doubt that God has been the single greatest influence on my theology (John 6:45).
Because of my experience with Adventism, I never read any of the authors and theologians some here have mentioned, save one, but I already knew what he was sharing. I read a little bit of Justin Martyr, too, but wasn't influenced by him. Other than the authors of the Bible, for much of my Christian experience, I feel I was beyond the influence of the commentators. I consider myself blessed for that reason.
Through fellowship on TOL, I have been influenced in one way or another, theologically and philosophically, by a number of people. Since I don't want to accidentally leave someone out, I will intentionally mention just two for reasons that will be apparent. The rest of you probably know who you are, and I thank you for helping me grow, too.
Without Knight I would not have been influenced through TOL because TOL would not exist. So in that sense, he has been one of the greatest influences in my theological development. God has used him mightily as a vessel for His glory through this forum ministry. His positions on judging and capital punishment are just two ways he's influenced my theology.
Perhaps the greatest influence on my theology, occurring six years ago, resulted from reading the posts of the one here best known as Sozo. God had shown me so much through my personal studies of the word, but when I read Sozo's views on the gospel and salvation everything I already knew came together for me, finally making sense, and I was subsequently converted.