Most recent is what is floating around the forum, sodium nitrate, nembutal, short drop suspension, full suspension hanging and carbon monoxide poisoning. As far as newest, well sadly the only research and development going into safely and humanely killing people has only been done with lethal injection and the death penalty, which is a combination of 3 drugs that are probably nearly impossible to get your hands on let alone self-deliver to your own death. Most of the right to die societies use nembutal I believe, or inert gas asphyxiation. I'd take a look at the method megathread compilation thread found here. https://sanctioned-suicide.net/threads/suicide-methods-megathread.4418/