Horace challenging Morgarath in the end of The Burning Bridge. He didn't really think it through, but by god, he looked BADASS.
Any time any/all of the main characters are put in charge of a force larger than 2 other people.
Will commanding the archers at the end of book 4, The Battle for Skandia, who happen to have previously been Skandian slaves. By the time the Temujai attack (which is about 2 weeks from when Will is given the archers) they are shooting at the full strength of a battalion of Araluen archers.
Hell, the entire battle for Skandia may be this. The Temujai expect to fight a horde of barbarians who they can curbstomp into the dust in a couple of hours. What they get in return is a well prepared and disciplined fighting force and a battalion of archers, who they rarely ever have to fight. It's mentioned the Temujai are the largest threat to the Western World, and they got beaten by a bunch of barbarians.