In a small bowl, mix together the sugar, salt, black pepper, cayenne, ginger and cinnamon; set aside. Pour the maple syrup into a large bowl and set aside.
In a large nonstick skillet, toast the walnuts over medium-high heat, stirring or shaking the pan constantly, until they are hot, about 5 minutes. Immediately add the nuts to the maple syrup and toss to coat. Stir in the spice mixture until the nuts are evenly coated. Spread the walnuts in a single layer on a rimmed baking sheet. Let cool completely before serving, about 20 minutes.