I've always been skeptical of the Trinity doctrine. I've felt like it was a doctrine that was created after the canonized Bible was already complete and was a "theory" about the relationship between God and Jesus.
I tend to lean towards modalism, I think of God as a singular being who assumes "roles" as Jesus and the Holy Spirit. The Old Testament seems to be very clear in many places about God's "oneness" and never implies a trinitarian nature. Jesus' divinity is obviously important for a Christian to accept, but I don't think the "three in one" concept is the only possibility. If you're counting all of God's appearances, why isn't the Angel of the LORD the fourth member, since He refers to God in the first person in His appearances?