using UnityEngine;
using System.Collections;

public static class Global      //Делать класс статичным (параметр Static в объявлении) не обязательно
{
           public static float Kot;
}
public class example : MonoBehaviour   
{
          //Основной код скрипта с именем example   
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour
  {
     void Update()  
    {
         ScriptName other;  
         other = gameObject.GetComponent("ScriptName") as ScriptName;
         other.DoSomething();
         other.someVariable = 5;
     }
}

using UnityEngine;
using System.Collections;

public class RaycastCam : MonoBehaviour   
{
   public GameObject Target;
   public RaycastHit hit;
   public Ray ray;
   void Update ()
   {
           if (Input.GetKeyDown (KeyCode.Mouse0))
           {
                 Raycast ();
            }
   }
   void Raycast ()
   {
          ray =  Camera.main.ScreenPointToRay (Input.mousePosition);
          if (Physics.Raycast(ray, out hit))   
          {
               if (hit.collider.name != Target.transform.name)
               {
                     Debug.Log (hit.collider.name);
                     Debug.Log (Target.transform.name);
                      Target = hit.collider.gameObject;
               }
         }
   }
}