To me, one of the greatest examples of a hero I've seen in my life is the unknown man who jumped repeatedly into the Potomac to save the people who went into the icy river in a plane crash. He rescued several people before succumbing to hypothermia. There are any number of reasons to believe he knew he wasn't going to make it out of there the last time, there weren't going to be any medals, nor public acclaim, nor even someone to shake his hand and say "Well done!" But he went in again anyway, trying to save people he didn't know from Adam. He never came out again; and we don't even know the man's name (at least, the last I heard, they'd never traced it down). Now that, to me, is a hero.
And for heroine? Try the mother who, when an abusive spouse went nuts one day and attacked their baby, threw herself in his way yet again (this was a woman who had grown up in an earlier day and had it in her head you don't leave a marriage), but this time he not only beat her (which had always been enough to keep the kid safe), but took a baseball bat and knife to her, then shot her in the chest, belly and head; then he went after the kid -- would have choked it to death except that the woman got up off the floor and wrapped herself around his neck until he lost his grip. Finally put the kid in a bag and stuffed it in the freezer, leaving them both to die. She managed to pull herself to a phone and call 911, but died before she could get out any information; he call prompted a visit, and the kid was found with minor bruises. The baby was less than 6 months old. Now, yes, she should have left him long before this; but in a day and part of society where that just didn't happen, what she did was nonetheless an act of heroism.
Or try the "carpetbagger" politician who came into the South (wish I could remember the man's name; he deservest to be remembered) and actually was trying to make Reconstruction work for all concerned. But because he was a carpetbagger, the KKK decided he had to die, so he was ambushed and shot 16 times (using the old musket balls), twice to the head, three in one leg, one in another, and ten times to the torso. They left him for dead; he crawled off into a ditch and lay there until he recovered enough strength the next day to crawl 3 miles to a house, where he was recognized and taken to a hospital. Infection had set in; he lost nearly half of his face, one eye, one leg and part of the other, and one arm. Congress was so outraged that they were about to undertake severe retributive justice, when the man had himself hauled into the chamber and argued the South's case. As a result, the guilty men were (mostly) found and sentenced to a life of hard labor, with the possibility of parol, no innocents were punished. Again; that's heroism.