Jason asked for a collection of 10 "must reads." I've restricted myself to Lutheran theological and devotional literature. If I were to expand this to include other confessions, then Schmemann and Pope Benedict XVI would be listed too.
Jacob's Elements of Religion (note: weak on the Supper; only fault I see in the book - well, aside from its horrible title. A patristically informed setting forth of a complete overview of Lutheran theology)
Krauth's Conservative Reformation (note: DENSE writing, but worthwhile. Any reader of this blog knows he's my favorite)
Gerhard's Sacred Meditations (The Lutheran classic devotional writing for all time; great way to spend Lent!)
Piepkorn's The Church (I wouldn't be a Lutheran today without Piepkorn's work - I'm very grateful for this collection of his essays)
Piepkorn's The Sacred Scriptures and the Lutheran Confessions (Ditto)
Sasse's We Confess Series (This is an essential collection; wonderfully translated by Dr. Nagel)
Sasse's Here We Stand (You'll never confuse Lutheran and Reformed again after reading this work)
Sasse's This is My Body (The definitive volume on Luther's contention for the Real Presence of our Savior's body and blood in the Eucharist)
Chemnitz' Ministry, Word, and Sacrament: An Enchiridion (In the Reformation, this and Rhegius were bound together to provide pastors a sort of workbook for doctrine and for preaching)
Rhegius' Preaching the Reformation (THIS is what they should be using to teach preaching at the seminaries!)
That's my list for the moment. If any others have "must reads," by all means, tell us about them in the comments.