function OnDrawGizmosSelected () {
    // Draws a 5 meter long red line in front of the object
    Gizmos.color = Color.red;
    var direction : Vector3 = transform.TransformDirection (Vector3.forward) * 5;
    Gizmos.DrawRay (transform.position, direction);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnDrawGizmosSelected() {
        Gizmos.color = Color.red;
        Vector3 direction = transform.TransformDirection(Vector3.forward) * 5;
        Gizmos.DrawRay(transform.position, direction);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnDrawGizmosSelected():
        Gizmos.color = Color.red
        direction as Vector3 = (transform.TransformDirection(Vector3.forward) * 5)
        Gizmos.DrawRay(transform.position, direction)