Make a dotted line from an object to the mouse 2d

pretty simple, use a line renderer:

(http://docs.unity3d.com/Documentation/ScriptReference/LineRenderer.html)

(http://docs.unity3d.com/Documentation/ScriptReference/LineRenderer.SetVertexCount.html)

 using UnityEngine;
 using System.Collections;
 public class test : MonoBehaviour {
 GameObject gun; // up to you to initialize this to the gun
      
     void Start() {
     LineRenderer lineRenderer = gameObject.AddComponent("LineRenderer") as LineRenderer;
     lineRenderer.material = new Material (Shader.Find("Particles/Additive"));
     lineRenderer.SetWidth(0.2f,0.2f);
     lineRenderer.SetVertexCount(2);
     }
      
     void Update() {
     LineRenderer lineRenderer = GetComponent<LineRenderer>();
     lineRenderer.SetPosition(0, gun.transform.position);
     lineRenderer.SetPosition(1, Input.mousePosition);
     }
     // Update is called once per frame
 
 }

you can add materials to them as well (such as a dotted line)

ok, I switched to c#... if you prefer, you can add this script to the gun itself, then change the 2nd to last line to read:

 lineRenderer.SetPosition(0, transform.position);

otherwise you need to set up the variable "gun" somehow, like with GameObject.Find for example