// Loads a random level
    Application.LoadLevel (Random.Range(0, Application.levelCount-1));

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        Application.LoadLevel(Random.Range(0, Application.levelCount - 1));
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        Application.LoadLevel(Random.Range(0, (Application.levelCount - 1)))