In no particular order:
In the Name of Jesus by Henri Nouwen--This is a life changing book that can be read in a little over an hour.
Contrarian Leadership by Sample--From the president of USC. Both creative and brilliant.
FISH--A tie for the best of the narrative management stuff. About creating positive moral in your life and the workplace.
Who Moved My Cheese by Spencer Johnson--The other good narrative management book. About adapting to change
Courageous Leadership by Bill Hybels--An awesome book on leadership by one of America's most influential pastors
Leadership and the One Minute Manager by Blanchard et al.--This encapsulates the brilliance of the One Minute Manager and the Principles of Organizational Leadership by Blanchard in one short book
Primal Leadership Goleman et. al--About using emotional intelligence as a leader. Most of this is based on solid research.
The Heart of Change by John Kotter (this is the only one I have not completed)--The star of leadership of the Harvard Business School. My favorite book by him is the difference between a manager and a leader.
The Rule of St. Benedict--A classic of a leader bringing order out of chaos in leadership
Honorable Mention: Because I have not read them yet
Good to Great--Collins
Becoming a Leader--Bennis