Edgar Derby - the thoroughly decent man who ends up being shot for taking a teapot. This reinforces the absurdity of war and the lack of fairness in it.
The diamond that Billy finds sewn in the lining of the child's coat he is given - he later puts it in a ring for his wife Valencia. Most readers and critics suggest that this coat probably belonged to a Jew - a child - who had been put in a camp; this would reinforce the idea of someone, through no effort of his own, benefiting from the misfortune of others. Billy is the most inept soldier in the world, but he always survives, and, as in this case, prospers.