Rotating2D

//Rotating transform to look at position in 2D
//There is no need to license for 3 lines of code I hope
//NOTE: This probably isn't the best solution performance-wise. It works pretty well tho.

void Update(){
    float rotationSpeed = 50; //If you want it to be instant, delete rotationSpeed and Time.deltaTime. Not tested, but should work.
    Vector3 pointInSpaceAroundWhichIWantToRotate; //Possibly the position of the body of your character.
    Vector2 diff = MousePosition2D () - (Vector2)transform.position;
    float angle = Vector2.Angle (transform.up, diff);
    Vector3 vec = Vector3.Cross (transform.up, diff);           //We need to determine the direction of diff. "transform.up" should be the way your character faces.
    if (vec.z > 0) {
        Char.head.transform.RotateAround (pointInSpaceAroundWhichIWantToRotate, Vector3.forward, angle * rotationSpeed * Time.deltaTime);
    } else {
        Char.head.transform.RotateAround (pointInSpaceAroundWhichIWantToRotate, Vector3.forward, -angle * rotationSpeed * Time.deltaTime);
    }
}

//NOTE: I use perspective camera in my 2D game, so I have to set the z position to 10. If you use ortographic, you don't have to do that.
Vector2 MousePosition2D(){
        Vector3 mousePos = Input.mousePosition;
        mousePos.z = 10;
        return Camera.main.ScreenToWorldPoint (mousePos);
}