iirc @Alen posted a picture of something that showed you the best way. Was it potassium cyanide?

Anyways, a shotgun to the head would deliver immediate results, but a mess for whoever your leaving behind. Hanging is slow and painful, falling, youll regret it on the way down, and the CO2 method of the car would work better if you put a hose from the muffler to the inside of your car.