function Update ()   
{  
    if (Input.GetMouseButton (0))   
    {  
        var ray = Camera.main.ScreenPointToRay (Input.mousePosition);  
        var hit : RaycastHit;  
        if (Physics.Raycast (ray, hit))   
        {  
            Debug.DrawLine (ray.origin, hit.point);  
            print(hit.collider.gameObject.name);  
        }  
    }  
} 
本代码未经实际测试！