In a small bowl, whisk together vinegar, sugar, and oil; set aside.
In a large skillet, cook bacon until crisp. Remove bacon, cut or crumble into pieces, and set aside. Pour off all but 2 tablespoons of drippings in pan (if there aren't enough drippings to equal 2 tbsp, add a little butter or oil).
Heat bacon drippings over medium-high then add shredded brussels sprouts. Cook, stirring constantly, for 3 to 5 minutes, or until just tender. Remove from heat and stir in bacon, walnuts, and dressing. Season with salt and pepper to taste.
Serve warm.