Leiter's put up a "top ten philosophy books or articles in last decade" post on his blog, and other blogs are doing their own specialized versions. I thought it'd be fun to follow the trend. Basically, write what you think might qualify to be among the top ten books or articles in philosophy of religion in the last decade (starting at 2000) and some reasons why it is important and worth reading.
Warranted Christian Belief's left a big impact; it is probably the most thorough defense of the justification, rationality and warrant of both theistic and Christian belief. (W/r/t warrant, it argues that there is no good de jure argument apart from a good de facto argument against theistic or Christian belief; w/r/t justification and rationality, it argues that there is no good de jure argument simpliciter.) This defense, as far as I've seen, has had little by way of strong objection in the literature. The book also outlines a detailed model for how Christian belief can have warrant. In addition, the chapter on defeaters is a good contribution to epistemology, and the chapter on pluralism has some of the earliest and (in my opinion) some of the best work on the currently hot topic of epistemic disagreement (it includes the now standard charge of self-defeat that equal weight viewers have to deal with). There is also the valuable material on the problem of evil.