// Instantiates a prefab with a random rotation at the world-origin
    var prefab : GameObject;
    Instantiate(prefab, Vector3.zero, Random.rotationUniform);

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public GameObject prefab;
    void Example() {
        Instantiate(prefab, Vector3.zero, Random.rotationUniform) as GameObject;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public prefab as GameObject

    def Example():
        (Instantiate(prefab, Vector3.zero, Random.rotationUniform) as GameObject)