Mix sugar, water, corn syrup, salt and butter in saucepan. Cook to 250 degrees (hard ball stage). Remove from heat; stir in vanilla. Pour in a thin stream over the popped corn, stirring constantly to mix well.
Shape with buttered hands into balls or any other desired shape.
If desired, you may also tint the balls different colors by adding food coloring to the syrup before it is poured over the popcorn. Makes 12 to 15 large balls.