Answer by diabloroxx

The correct syntax for Instantiate is : Instantiate (original : Object, position : Vector3, rotation : Quaternion) : Object You have supplied arguments like (Object,Vector3,Vector3) . It should have been Quaternion.

var hitParticle : GameObject;

function OnCollisionEnter(collision : Collision) {
   for (var contact : ContactPoint in collision.contacts) {
      var Hit = Instantiate (hitParticle, contact.point, Quaternion.identity);
   }
}