Moving 2D collider and lag

Just wondering what is an efficient way to have a 2D collider and animation/movement script on an object without huge lag issues, in this example I have a rotating saw blade on a sprite that moves up and down and kills the player on collision. Closest possible solution is moving the rigidbody itself but wondering if there’s another simpler solution?

Just reposting answer here to answer thread:

 //Ball and chain rotation trap
 private var rb2D : Rigidbody2D;
 function Awake() {
     rb2D = GetComponent.<Rigidbody2D>();
 }
 function FixedUpdate () {
     rb2D.MoveRotation(rb2D.rotation + (-speed*10) * Time.fixedDeltaTime);
 }

or a similar situation to shoot an arrow for example

 public var arrow : GameObject;
 public var speed : float = 3;
 function SpawnArrow () {
     var arrowProjectile : GameObject = Instantiate(arrow, transform.position, transform.rotation);
     arrowProjectile.GetComponent.<Rigidbody2D>().velocity =
  (arrowProjectile.transform.right * speed);
 }