[pie]

Ну тогда так уж.

public Camera cam;

void Update () {
		
		Ray ray = cam.ScreenPointToRay (Input.mousePosition);
        RaycastHit hit = new RaycastHit();
        if (Physics.Raycast (ray, out hit))
        {
            Vector3 rot = transform.eulerAngles;
            transform.LookAt(hit.point);
            transform.eulerAngles = new Vector3(rot.x, transform.eulerAngles.y+90, rot.z);
        }
		
	}