Get raycast direction from weapon

I want to use raycast to create a laser system (also for the bullets) for the weapons in my game, but right now Im just trying to draw a line to see whats going on in there. But how can I get the direction where the weapon is pointing?

using UnityEngine;
using System.Collections;

[AddComponentMenu("Rayco's scripts/Laser")]
public class laser : MonoBehaviour {
	public GameObject weapon;
	public Vector3 RotationOffset;
	public Vector3 PositionOffset;
	Vector3 rayo;
	Vector3 direccion;
    void Update() {
		direccion = weapon.transform.forward;
		rayo = weapon.transform.position;
        transform.parent = weapon.transform;
        Physics.Raycast(rayo, direccion, 10);
         Debug.DrawLine(rayo, direccion, Color.red);
    }
	void start() {
		transform.localEulerAngles = RotationOffset;
		transform.localPosition = PositionOffset;
	}
}

As Wolfram mentioned, there are a number of issues with your code. So below is a bit of starter code. Attache the script to your gun (or a child object of your gun), drag a light onto the public lightLazer variable, and the script will place a light on objects the Raycast hits in the scene. I setup my light with a range of 0.1, intensity of 1.5 and the color red. This code cast the ray from the origin of the object it is attached to. You will need to translate the ray up to the gun sight level (or perhaps easier, attach the script to an empty game object with its origin at the level of the sight). Also if your gun has a collider, you will need to either 1) remove it, 2) use a more complex raycast, or 3) move the origin of the raycast outside the gun. Good luck with your project.

using UnityEngine;
using System.Collections;

public class Lazer : MonoBehaviour {
	
public Light lightLazer;
private Ray ray;

	void Start ()
	{
		lightLazer.enabled = false;
	}
	
	void Update ()
	{
		RaycastHit hit;
		ray.direction = transform.forward;
		ray.origin = transform.position;
		if (Physics.Raycast (ray, out hit))
		{
			Vector3 v3Pos = ray.GetPoint (hit.distance * 0.995f);
			lightLazer.enabled = true;
			lightLazer.gameObject.transform.position = v3Pos;
		}
		else
		{
			lightLazer.enabled = false;
		}
	}
}