Lightbringer at its most useful (Spoilers Published)
Davos reading the Night's Watch letter by the glow of Stannis's sword is such a good little detail.
I'd remembered the argument over Edric and the letter changing the direction of Stannis's campaign. Somehow I'd forgotten how those things are physically staged. Davos has sent the boy away. Stannis draws Lightbringer. Davos kneels, unfolds his parchment, and uses the light from the weapon threatening him to read an appeal for help.
For a moment, the sword of prophecy is a reading lamp.
What makes it work for me is how much ordinary effort sits behind that moment. Davos has been taking lessons with Pylos because he thinks the King's Hand ought to be able to read. That's a fairly modest ambition for a character in a story full of inherited swords, secret bloodlines and prophetic dreams. Then it pays off at exactly the point when he needs to give Stannis something useful to do.
He's already protected one boy by getting him onto a ship. Now he puts the needs of people at the Wall in front of the king. Stannis has a chance to act on a request from men who are actually asking for his help.
And the big glowing symbol of his destiny is sitting there illuminating the words.
I find that more satisfying than a lot of the speculation about what Lightbringer might eventually turn out to be. Whatever the sword's magical status, this particular use of it helps set an army moving toward the Wall. There's something very Davos about getting practical value out of an object everyone else is arguing over.