O'Flaherty's sniper character certainly fits the description of a fanatic. A fanatic is someone who is "marked by excessive enthusiasm and often intense uncritical devotion" (Merriam). His fanaticism is shown in several ways. First, the story begins by alerting the reader that the sniper had been camped on top of the building without any comfort and relief. He then looks below and sees an woman alerting an enemy vehicle about his position. Withouth hesitation, he cooly shoots the man in the vehicle, but he then also kills the woman, a citizen who is not a soldier of war.
His cunning is shown in how he tricks the enemy sniper into believing he had killed the protagonist. He does this by putting his cap on top of his rifle and pretending to be killed when the enemy sniper puts a bullet into the empty hat. This allows the sniper to stand, pull his revolver, and shoot the enemy sniper who falls to his death.
Courage can be defined differently. The sniper shows some courage by simply fighting for what he believes in during the Irish civil war. Some may say his killing of the enemy in the vehicle and the woman who gave away his position. The most obvious example of courage is how the sniper is able to kill his enemy even though he is already wounded from a gunshot to the arm.