Richard Kirkland of South Carolina
During the Civil War's Battle of Fredericksburg in December 1862, Kirkland was posted on a bluff called Marye's Heights, behind a stone wall on the left (north) side of Lee's line above a sunken road and plain. Union forces under new commanding general Ambrose Burnside charged that wall incessantly during the three days of that battle, to absolutely no result but the wholesale slaughter of thousands of Union troops.
Kirkland took pity on the men lying in that plain before him, and asked permission of his CO to go aid them. The CO, after asking his commanding general (who replied, paraphrasing, if the fool wants to get his ass shot off, fine), allowed him to go. Kirkland filled up several canteens with water, and then set off into no man's land. For 90 minutes, Kirkland crawled across that field, offering water to the injured enemy troops, attempting to ease their pain, or even just praying with them. Union soldiers on the other side of the line, seeing what Kirkland was doing, avoided intentionally shooting at him, and he miraculously managed to avoid the crossfire. For this selfless act of mercy, Kirkland was nicknamed "The Angel of Marye's Heights."
Kirkland died 10 months later, at the Battle of Chickamaw in Georgia. Some years later, a statue, nearly five times lifesize, was erected to Kirkland by grateful Union veterans who remembered his actions in Fredericksburg.