I'll go ahead and bite:
Philisophy/FictionAtlas Shrugged by Ayn Rand. Who
is John Galt? Another book I try to read regularly. It is a truly hefty read, but once you get some momentum it moves quickly. I put this at the top of my list as its warning is becoming more and more relevant to modern politics and society. A tale of how heavy-handed government both stifles innovation and hope and drives great men and women to lives of seclusion instead of contribution.
Fantasy:The Once and Future King by T.H. White. I'm not much of a fantasy reader outside of Tolkien, but I read this book when I was 9 and I still try to read it once a year. It's fantasy, but written around the myths of King Arthur, so it has a familiar feel, yet the writing is out of this world.
ThrillerThe Lost Symbol by Dan Brown. I know, it seems like a bit of a punt to pick something off of the current best-seller lists, but this was my favorite Brown book. It's not his best work--most quasi-intelligent readers know where it ends within the first couple of chapters and the last couple of chapters are drivel in my mind, but the subject matter is riveting to me as a US history buff. Brown has an uncanny ability to draw connections between facts and events, and the Americana in this book is must-read material. Just leave Jesus alone already though.
HistoryA Terrible Glory by James Donovan. The most objective and informed look at Custer and the Battle of the Little Bighorn I have read to date. A sobering look at the politics and hubris within the post-Civil War American Army.
The American Revolution by John H. Rhodehamel. For the true American Revolution buff, this is a must-read. It is not a book so much as a collection of original writings. You learn about Lexington and Concord from the journals of the Redcoats who were harrassed along the highway and you read their fear and indignation about the guerilla tactics. Nothing beats firsthand, as shown by the popularity of McCullough's stuff lately. This book is hard to find, and a bit pricey, so look for it in a library (BYU has it).
MoralityThe Very Persistent Gappers of Frip by George Saunders. Another out of print book, but a great parable for adults and children. It's a short book (think Max Lucado books) with terrific illustrations, but teaches the virtues of work, persistence, charity and accountability.
FWIW, here's my goodreads:
http://www.goodreads.com/review/list/1319499