Quaternion.identity

The identity rotation (Read Only). This quaternion corresponds to "no rotation": the object

is perfectly aligned with the world or parent axes.

JavaScripts

transform.rotation = Quaternion.identity;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
transform.rotation = Quaternion.identity;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
transform.rotation = Quaternion.identity