This works best with a medium hot grill. Take one unpeeled banana and split the skin along the center, taking care to leave the ends uncut. Spread the skin apart a bit and add each topping about a 1/2 teaspoon at a time: mini marshmallows, chocolate chips, butterscotch chips, chopped nuts, chopped candies.
Place on a sheet of foil and loosely close ends together. Place on the grill until toppings have melted. About 2-3 minutes. Carefully open foil and enjoy with whipped topping.