Trying not to appear unspiritual for not crediting the Holy Spirit... but I have been influenced by Chuck Swindoll's books and Lloyd Jones sermons on Romans.
James M. Boice from 10th pres in Philadelphia has also been influential.
The Holy Spirit is the Author of the scriptures.
He has had the "most" influence on me.
I really can't say any human theologian has had much influence on me because I don't read theological books.
There are certain men of God that have had an influence such as my pastor, Adrian Rogers, Charles Stanley, but the Bible is my main source.
David Jeremiah
Randy Alcorn (not for theology, to to re-mold my thinking on Heaven away from a strumming-a-harp-on-a-cloud mentality to one of reality.)
Carlyle Marney wrote a number of books. Those I remember as the moment are:
Faith In Conflict
The Coming Faith
Priests To Each Other
The Carpenter's Son
Dangerous Fathers, Problem Mothers and Terrible Teens
Beggars in Velvet
Crucible of Redemption
He Became Like Us
Structures of Prejudice
I doubt any of his book are still in print but I am sure you can buy used ones online.