There are a few that I come back to year after year. THE ART OF WAR, of course. Bruce Lee's THE TAO OF JEET KUNE DO. George Leonard's MASTERY. Joe Hyams' ZEN IN THE MARTIAL ARTS. Brian Enos' PRACTICAL SHOOTING: BEYOND FUNDAMENTALS. Jeff Cooper's PRINCIPLES OF PERSONAL DEFENSE.
Novel-wise, I have read Jerry Pournelle's THE MERCENARY and its sequels more times than I can remember. I read the whole sequence, gathered in a single volume titled, appropriately, THE PRINCE, a few months ago and I it moved me as much or more than when I first read it so many years ago. I go back to Raymond Chandler (usually THE LITTLE SISTER or THE LONG GOODBYE) over and over again, and occasionally Dashiell Hammett's RED HARVEST. I can still recite chunks of Albert Camus' THE PLAGUE; I also recently went back to the Robert Ruark Africa novels.
Every couple of years I reread Stephen King's THE STAND to remind myself that while evil never truly dies, we all have the opportunity to stand.
Finally, every Christmastime for the last few years I have watched all 13-some odd hours of the Lord of the Rings trilogy in a single sitting. This usually involves adult beverages.
Michael B