CODE EXAMPLE FOR CSHARP

unity 2d looka tt mouse

void Update() {
     Vector3 dir = Input.mousePosition - Camera.main.WorldToScreenPoint(transform.position);
     float angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg;
     transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);