Raw Source
BskyB / Open any YouTube video in Gaming mode 

// ==UserScript==
// @name        Open any YouTube video in Gaming mode
// @icon        http://i.imgur.com/vD67sda.jpg
// @namespace   http://userstyles.org
// @author        BskyB
// @description	  Opens any youtube video in gaming (https://gaming.youtube.com/) mode. other pages like http://www.youtube.com/feed/subscriptions will open in their default desktop view. Works for both regular and live videos of any content not only gaming
// @version	2015.09.03
// @include        https://www.youtube.com/watch*
// @exclude     https://www.youtube.com/tv#/watch*
// @exclude     https://gaming.youtube.com/watch*
// @homepage      https://userstyles.org/styles/118163
// @grant       GM_getValue
// @grant       GM_log
// @grant       GM_openInTab
// @grant       GM_registerMenuCommand
// @grant       GM_setValue
// @grant       GM_xmlhttpRequest
// @grant       GM_addStyle
// @run-at         document-start
// ==/UserScript==

//Redirect from standard Youtube to TV view
window.location.replace(window.location.href.replace("https://www.youtube.com/watch","https://gaming.youtube.com/watch"));