One of my friends is on a mission trip to Peru, and he just sent me an email about how God used him to miraculously heal a woman who had been partially paralyzed in a stroke. We won't know the complete details of this spiritual encounter until he returns to the States, but from his description, God is the only explanation for her healing, and other people came to know Jesus because of it. My friend confessed that when he began to pray, he didn't possess some monumental faith. He just asked Jesus to heal her body, and the Lord obliged.
My friend's experience is an example of how God chooses to use the prayers of his saints to do the impossible, even in spite of our sinfulness and unbelief. But even though God is gracious enough to let us take part in his work, he doesn't need us to get things done.
In China and other parts of the world where the supernatural encounters are a way of life, God often uses visions to get people's attention. People will often describe a dream in which Jesus came to them--without any intermediary--and called them to believe. Paul, the apostle formerly known as Saul, had a blinding vision of Jesus on the Damascus road that led to his conversion and his subsequent commission as missionary to the Gentiles. In each of these encounters, God dealt directly with the people he wanted to use for the furtherance of his kingdom.
Later in Paul's ministry, he was performing miraculous signs in Ephesus, a town famous for its temple to the Greek goddess Artemis. He often went to the synagogue to reason with both Jews and Gentiles, attempting to convince them from the scriptures that Jesus really was the Christ. He was widely renowned as a teacher, and he was well-respected among the people, so much so that the his ministry threatened the livelihood of the silversmiths, who made their money crafting idols for Artemis worshippers. Some sons of a Jewish high priest decided it would be fun to use Paul's authority cast out a demon. Because they didn't have Jesus' authority within them, the demon didn't respond in fear. He basically said, I know Jesus and Paul, but you don't mean anything to me. Then the demon, who indwelt one man, took on all seven of them and sent them bleeding and crying back to their daddy.
But here's why I cite this obscure story. As a result of the incident, the fame of Paul, Jesus and the Father spread throughout the city, and the town's sorcerers got together and had a good old-fashioned scroll-burning party. Because they feared God, they set their magic spells on fire, and many of them believed in Christ. In this incident, Paul didn't do anything. No faithful apostle came and explained the wonders of the Gospel to these sorcerers. God himself used a demonic beat-down to effectively end the practice of sorcery in Ephesus and draw some high-ranking officials to himself.
Never approach God thinking that he needs you to accomplish his work. Ask him to allow you to be a part of it, and he will, but remember that he's always the director and the star of the show. For him to give us bit parts in this great drama is more than we deserve and enough to thank him for. We're expendable, but somehow, in his great wisdom and grace he counts us as dependable. Appreciate this privilege and when he calls you, don't let him down.