James D.G. Dunn, The Theology of Paul the Apostle
Required reading for most PhD programs and rightly so. It was difficult not to include Sanders' Paul and Palestinian Judaism here; that book certainly represents a sea change in New Testament studies. But if I had to recommend only one of these "new perspective" books, I'd recommend Dunn's opus. The Theology of Paul the Apostle set the standard by which all books on Paul would be measured (and still are). Also, he writes job letters for me, so I have to say nice things.
Craig A. Evans, Ancient Texts for New Testament Studies
This book was formerly titled Noncanonical Writings and New Testament Interpretation. The more recent version is worth the additional purchase. Ever get mixed up on the difference between the Talmud and the Targums? Fearful of sticking more than a toe into the waters of Dead Sea Scrolls research? And what's the date on the Shepherd of Hermas again? This book is the best introduction of the vast sea that is Second Temple (and thereabouts) Jewish (and contemporary) literature. But the real reason that you want this book is for the scriptural, cross-listing index. Evans lists hundreds of parallels between the New Testament and contemporary literature - of course, it is up to the reader to decide how to use such parallels.
Susannah Heschel, The Aryan Jesus
Modern biblical studies is rooted in German Protestantism. So many of our default positions come from a time and place that is now quite alien to us (I speak here as an American who was educated in Canada and the UK). Heschel's book is a brilliant introduction to these default positions. Time will tell whether her book becomes a standard classroom text, but it should.
E.P. Sanders, Jesus and Judaism
I don't go in much for "Quest" demarcations, but it cannot be denied that Sanders led the charge on the most productive era of Jesus research in history. Honorable mention goes to Geza Vermes for his Jesus the Jew. Who wouldn't want to read what Sanders, the greatest living New Testament scholar, has to say about Jesus?
Albert Schweitzer, The Quest of the Historical Jesus
Much like Bultmann (see Chris' list), Schweitzer's voice still sets the tone for the choir. Although we've nuanced his Quest paradigm a great deal, it is still his work that provides the basis for the field.
Klyne Snodgrass, Stories with Intent
Best and most comprehensive book on the parables ever written. And I remain a big fan of Jeremais' masterful treatment. You simply will not have access to the earliest memories of Jesus unless you understand how the parables work. Snodgrass' book might provide the best window into this seminal thoughtworld.
N.T. Wright, New Testament and the People of God
This book (remarkably) has been overshadowed by his Jesus and the Victory of God. I almost wish that the second of these was never written. NTPG, when measured on its own, is epochal. Even if one disagrees with the overarching program, this book has generated more talking points in our field than any other in the past fifty years.