Gunshot and maybe hanging, too, because of the somewhat grim sight when found. As well as unnecessarily painful and grim methods like burning and electricution. In my view they are just not really ways to go with most dignity. I understand and respect that a lot of people won't care what the body will look like, but to me I find it matters somewhat.
Personally I would also perhaps steer away from methods that pose an increased chance of harming others like jumping (possible, but unlikely physical damage but possible emotional trauma when found), carbon monoxide, hydrogen sulfide and some of the lethal inorganic salts. And unreliable methods like many/most drug overdosings.
I think I would only really do inert gas, nembutal and maybe sodium nitrite, of which inert gas is my current method of choice if the time comes. :)