The CO2 stuff isn't a good way to go at all. There's too much that can go wrong and it takes longer than just chopping the head off or breaking the neck. Quite frankly, if you can't handle having to put something down emotionally or whatever, then maybe animals like this aren't for you. What's best for the animal is very rarely what's easiest/least "traumatic" for us, that's all there is to it. Personally, I wouldn't want to die by suffocation or poisoning of any sort, doesn't sound all that pleasant to me. I've seen what bigstack was talking about, and I'm not easily disturbed, but that scene bugged me big time. I had a neighbor that used to put all his animals down like that, trust me, they didn't just peacfully fall asleep.