Should collision detection be enabled? (By default always enabled).

Disabling collision detections is useful when you have a ragdoll which is setup to be kinematic and you want to avoid heavy collision detection calculations on that rigidbody. detectCollisions is not serialized. This means it doesn't show up in the Inspector and when Instantiating the rigidbody or saving it in a scene, it will not be saved.

	// Let animation control the rigidbody and ignore collisions
	rigidbody.isKinematic = true;
	rigidbody.detectCollisions = false;
	// Let the rigidbody take over control, detect collisions 
	rigidbody.isKinematic = false;
	rigidbody.detectCollisions = true;

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        rigidbody.isKinematic = true;
        rigidbody.detectCollisions = false;
        rigidbody.isKinematic = false;
        rigidbody.detectCollisions = true;
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		rigidbody.isKinematic = true
		rigidbody.detectCollisions = false
		rigidbody.isKinematic = false
		rigidbody.detectCollisions = true