Snuff.. what's not to understand about it? Its small pieces of tobacco and other herbs blended together that is sniffed up the nose...
Oh, hang on... you mean the *other* type of snuff...
Not heard much about this in the BDSM scene, and then only as stories rather than real life. Mostly only heard about it in horror videos. Of course one reason you may not have heard about it is the fact that it is horribly and totally illegal. IMO it also breaks all three elements of safe, sane and consensual (even if the person consents to being killed I am not sure should be possible to consent to your own death, it certainly isn't legally and morally it is a nasty area of personal freedom to explore).
Having said that, of course, I am in favour of euthanasia because I think someone with a terminal illness who wants to die due to extreme pain should be allowed to do so with dignity rather than being forced to stay alive. Legally, even this would get the killer a life sentence for pre-meditated murder (though most judges seem to defer it to manslaughter due to the mitigating circumstances) However, consensual killing for pleasure of an individual or videoed for the pleasure of others? Not a chance...