How to damage gameobject via raycast

Hi i'm looking the best way to apply damage via raycast.

using this script, I know the tag gameobject hit, but how can I apply damage?

I have many gameobject with the same tags.

i need other script attached gameobject enemy?

SendMessage can be the solution? how to use this?

     var shoot: GUITexture;
     public var camera1:Camera;
     var crosshairs:Texture;
     
 
     
     function Awake(){
     shoot= GameObject.Find("shoot").guiTexture;
     
     }
     
     function Update () {
     
     for(var touch : Touch in Input.touches){
     if(touch.phase == TouchPhase.Ended && shoot.HitTest (touch.position))){
     animation.Play("shoot");
     audio.Play();
     ShootFunction();
    }
     }
 
 function OnGUI() {
      GUI.DrawTexture(new Rect(Screen.width / 2, Screen.height / 2, 50, 50), crosshairs);
 }
 
 function ShootFunction()
     {
         var ray : Ray = camera1.ViewportPointToRay (Vector3(0.5,0.5,0));
         var hit:RaycastHit;
         if (Physics.Raycast(ray, hit)){
          Debug.Log("Hit " + hit.collider.tag);}
         
     }