In this article on CNN, Dr. Francis Collins, a microbiologist and director of the Human Genome Project, explains how he can be both a scientist and a believer in the Christian God. He argues that science isn't able to answer questions like "what is the meaning of life," or "what happens after we die?" In searching for answers to these questions, Collins converted to Christianity.
Strangely enough though, Collins seems to refute his own argument in the following quotation:
"Faith is reason plus revelation, and the revelation part requires one to think with the spirit as well as with the mind. You have to hear the music, not just read the notes on the page. Ultimately, a leap of faith is required."
Basically what Collins is saying, then, is that it is in fact not possible to make a scientific, rational decision that the Christian God exists. Instead, the decision must be made in the face of a complete lack of evidence (hence the required "leap of faith"). The scientific method is concerned with the observation of evidence, and faith is belief in spite of (or because of) a lack of evidence. Otherwise it wouldn't be called faith. As we can see then, Collins made an unscientific decision to convert to Christianity. He admits as much himself.
In one of the comments that follows, Alan Goldstein says it best:
"As is typical of believers, Collins was looking for answers, and when he didn't find them (or more likely didn't care for the answers he found), he turned to superstition. For example, what is the meaning of life? Science would say "Life has no meaning, other than the meaning we give to it." I think this is a wonderful answer, and immensely preferable to, life exists because god was bored. And that our sole purpose for existence is to please god enough, so that we may enter heaven and sing his praises for all eternity."
It's really unfortunate that a man who holds such a prestigious position would abandon the rational morals of his profession because he did not care for the answers they provided, however stark and rigorous they may be. What a loss.
Oh well. To make you feel better, here's a graph showing who killed the largest number of people in the Bible.