Problem with collision - Collision.other.gameObject is obsolete

Hi all! Got a problem with a script!

I got an enemie that when it's hit by either a laser or a missile from my player, it's take a certain amount of damage and it's based on the tag of the colliding object.

Before you could just use Collision.other.gameObject.tag for the other colliding object (in this case either my laser or missile) But now it's OBSOLETE!!!!!

Unity says to use Rigidbody or Collider but i dont know hell how to do that!!! Here's my code any help would be great!! How do you refer to the other colliding object???

 #pragma strict
 public var startingHealth : int =5;
 private var enemyHealth : int;
 
 function Start () 
 {
     enemyHealth = startingHealth;
 }
 
 function Update () 
 {
     CheckHp();
 }
 
 function Hit(damage:int)
 {
     enemyHealth -= damage;
     Debug.Log("Taking DMG");
 }
 
 function CheckHp()
 {
     if(enemyHealth <= 0)
     {
         Destroy(gameObject);
     }
 }
 
 function OnCollisionEnter(collision : Collision )
 {
     if(collision.other.gameObject.tag == "Plaser")
     {    
         Debug.Log("Ouch");
         Hit(2);
     }
     
     if(collision.other.gameObject.tag == "Pmissile")
     {    
         Debug.Log("Ouch");
         Hit(5);
     }
 }