Run script when object is clicked

Hi and welcome to Unity Answers :) I would raycast from the camera. like so:

 // This holds the info on what we hit
 RaycastHit hit;
 // find your camera and convert your mouse position to a ray
 Ray ray = Camera.current.ScreenPointToRay(Input.mousePosition);
 // rayCast into the scene And require that something is hit has a transform
 if (Physics.Raycast(ray, out hit, Mathf.Infinity) && hit.transform != null)
 {
     // try to retrieve classA from the script
     ClassA tmp = hit.GetComponent<ClassA>();

     // did we hit something with the script on it? 
     if (tmp != null)
     {
         // if so.. Fire the missiles! 
         tmp.LaunchScript();
     }
 }