Allows you to have infinite ammo (via the SMS and Equips MFD pages), equips from any vehicle on any playable vehicle, and the ability to shoot multiple guns at the same time (also the the SMS and Equips MFD pages). If you want to just download a release, here would be the best place to do so.
If you're here for the list of available equips, here you go, it's located in Equip Constants, with proper commenting now.