Matador Series by Steve Perry
Emile Khadaji was a soldier for the Galactic Confederation until a decisive battle awoke his disgust of war. He wandered for a time and found himself under the tutelage of a man called Pen who showed him a new way of living. Khadaji found other teachers along his path and eventually found a new mission, one that challenged the Confed directly in a unique fashion. The Man Who Never Missed is a great science-fiction adventure that also delves into the nature of a warrior.
This is the first book in a 3 part gritty sci-fi series. I would rate them as can't put em down until they are done. Excellent character development, cool futuristic setting and amazing feats of daring from a Robin hood type of guy.