Enchiladas are a delicious way to use up leftover rotisserie chicken. Simply shred the chicken and mix it with some shredded cheese and diced onions. Roll the mixture up in some tortillas and place them in a baking dish. Top with some enchilada sauce and more shredded cheese. Bake in the oven for about 20 minutes, or until the cheese is melted and bubbly. Serve with some sour cream and guacamole.