Transform.localRotation

Description

The rotation of the transform relative to the transform rotation of the parent.

Unity stores rotations as Quaternions internally. To rotate an object, use Transform.Rotate. Use Transform.localEulerAngles for modifying the rotation as euler angles.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    void Example()
    {
        transform.localRotation = Quaternion.identity;
    }
}

Another example:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// Rotate a cylinder around the x and z axes. Switch from one to the other
// when the rotation in the current axis reaches 360 degrees.

public class ExampleScript : MonoBehaviour
{
    private float x;
    private float z;
    private bool rotateX;
    private float rotationSpeed;

    void Start()
    {
        x = 0.0f;
        z = 0.0f;
        rotateX = true;
        rotationSpeed = 75.0f;
    }

    void FixedUpdate()
    {
        if (rotateX == true)
        {
            x += Time.deltaTime * rotationSpeed;

            if (x > 360.0f)
            {
                x = 0.0f;
                rotateX = false;
            }
        }
        else
        {
            z += Time.deltaTime * rotationSpeed;

            if (z > 360.0f)
            {
                z = 0.0f;
                rotateX = true;
            }
        }

        transform.localRotation = Quaternion.Euler(x, 0, z);
    }
}