All three songs the Sorting Hat sings during the story are Crowning Moments Of Awesome for the Hat, each in different ways (though none of the characters in the story apart from Peeves would agree that the first one is). Not because the songs are so awesome in and of themselves, but because of what they accomplish.
Dewey gets one when he stands up to Harry and Ron, who want to get them to safety before evacuating the House-elves, and then leads a group of other students to go in and rescue the elves:
"It's not right, saying our lives count more than theirs." He swallowed. "I know you can stop us, sir." And then he looked behind him, at the other pale, trembling firsties, and gestured. He marched forward, towards the stairs down to the kitchens, and the others followed, all looking fearfully at Harry and Ron. Nagaeena, bringing up the rear, gave them a pleading look. She obviously wanted Harry to stop them. But he didn't. He was looking at Ron. "Are you feeling as ashamed as I am?" he asked. "Yup," Ron replied.