I think I would have to pick the 21st chapter of John. I have been restored over and over again by this. I have been where Peter was. I know the feeling of rejecting Christ to pursue... what ever. Some times we can reject him inadvertantly and realizing it later in life when we realize we screwed things up. When that happens the Holy Spirit convicts and brings us to repentance and at that point God restores us.
Imagine the shame Peter felt the sitting on the shore. The savior had came to HIM, he was there with all of them, but he came with the express reason to speak to Peter.
Do you love me Peter ? Do you love me Peter ? Do you love me Peter !? Then stop feeling sorry about the denial, and get up and do what I asked you to do ! Obviously I'm paraphrasing here, forgive me. But this is exactly how God spoke to me this past year through this chapter. I felt so mortified about this colossal failure in my life, that I could scarcely breath. Depression was physically painful, and I was an emotional wreck. My spiritual life was very week, and I just couldn't bring my self to care about ANYTHING ! Then... one morning as I lay in bed after work, I picked up my Bible and began to read this 21st chapter. Immediately I began to sense God's presence. I continued to read. "Do you love me Jayson ?", "Then stop feeling sorry for yourself". "Stop feeling sorry for yourself and do what I asked you to do !" You see, I had to learn that Satan is the accuser of the brethren, not God. These feelings of guilt and shame were not of God, and this passage helped me to see that. God forgives ! Because he loves us, and called us, and the gifts and callings of God are unrepentant. So, again, i ask you... if you had to choose just ONE passage, what would it be, and why ?