If I ever want to off myself then it's nitrogen for me. The thing that makes the nitrogen leak so dangerous is that you don't realise you are dying. It is like turning off the oxygen on a rebreather, you just fade away. This was demonstrated on TV by Jonathan Miller, in the days before political correctness, so we would all know how to off ourselves painlessly. Be sure to leave a note on the door.
I use it for the plasma cutter because it is dry, something that plasma cutters really seem to appreciate for some reason known only to plasma cutters and plasma cutter geeks. Perhaps air guns would also prefer dry? It is also very cheap