Dragon Age: Origins - The Stone Prisoner

I'm not simply giving this DLC a 10 because it's free, but the character that is primary focus of the DLC is arguably one of the best companions in the series, and compared to how other games handle their paid DLC companions, Origin's free DLC companion actually receives the same depth as the base game's characters, complete with their own unique equipment, dialogue tree, abilities and subplot, and the character even has significant ties to the narrative.