Unscrewing screws without the use of a screwdriver

Does anyone know how to unscrew a screw without using a screwdriver? What can one do if the inside of the screw is accidentally smoothened during assembly making it impossible to remove the screw using a screwdriver?

The two best tips I have for removing a stripped screw are:

  1. Use a Rubber Band to try and generate the needed grip to loosen the screw. I recommend doing this first, as it is by far the simplest way to solve this problem but It might not work with screws requiring high torque to remove.
  2. Apply a small amount of superglue to the screw and attach a nut to the top. After the superglue dries you can attempt to remove the screw by turning the attached nut. For this method you need to be careful with the glue, both to avoid accidentally gluing the screw in permanently and to be sure the glue will hold the nut in place.