You probably have a bunch of components that you want to keep a constantly updated list of too. Maybe all your enemies, or maybe all your bullets. (For Unity3D engine, from http://garry.tv/2015/06/14/unity-tips/)

ListComponent.cs

using UnityEngine;
using System.Collections.Generic;

public abstract class ListComponent<T> : MonoBehaviour where T : MonoBehaviour
{
	public static List<T> InstanceList = new List<T>();

	protected virtual void OnEnable()
	{
		InstanceList.Add( this as T );
	}

	protected virtual void OnDisable()
	{
		InstanceList.Remove( this as T );
	}

}