Rigidbody.angularDamping

Description

The angular damping of the object.

Angular damping can be used to slow down the rotation of an object. The higher the damping the more the rotation slows down.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public Rigidbody rb;

    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    // Get a wild spin under control when the user
    // presses the spacebar.
    void Update()
    {
        if (Input.GetKeyDown("space"))
            rb.angularDamping = 0.8F;
        else
            rb.angularDamping = 0;
    }
}