A fetish film, sometimes pornography, in which the slow process of someone being tortured and killed is committed to video tape. The basic snuff film has a subject, usually an abductee, who is tortured with various instruments of mutilation for most of the duration of the film. The film often ends with the final "snuffing" of the victim in a savage orgy of carnage (sometimes chainsaws are used). By this time he/she may already be disemboweled and the chest cavity may be fully open (before the victim is finally snuffed), and the other participants may commit acts of further perversion with the vital organs of the victim.
The unreleased Broken movie by Nine Inch Nails was reported to contain clips from a snuff film, prompting authorities to conduct an investigation.

According to the FBI, snuff films are an urban legend. They may exist, but the FBI has yet to find any authentic ones. "Snuff" films are fakes passed off as or mistaken for the real thing. Nicholas Cage watches a lot of these fakes in 8mm, and even most of the porn freaks he talks to say there's no such thing.

Nine Inch Nails's unreleased long-form video for the EP broken was a take on a snuff film. It's not real, but it's really grainy, and, unlike The Blair Witch Project, actually increased the feeling of reality while watching the film.

Really, really, really, graphic stuff. Faces of death, even the non-faked scenes, ain't got nothin' on this.

For a more hi-fi and artsy type, see Bob Flanagan in the video for NIN's Happiness in Slavery. Flannigan is also the focus of the biographical documentary "Sick" (full title: Sick: The Life & Death of Bob Flanagan, Supermasochist), which you can find at better video stores near you. It's actually a very interesting look at the relationship between Bob and his wife (who did many of the acts upon him). Mr. Flanagan passed away from Cerebral Palsy (I think). I'll double check that and update later.

Updated Nov. 6, 2002:
Due to a deluge of messages, I feel I should clarify my original definition of a snuff film. Here's a run down:

Snuff films are:
• Murders commited for the sole purpose of filming the act with the intent to sell the resulting video. (Or if not to sell, then at least for an audience.)
• Snuff films are pornographic. This is not to say they must include sex, but that the ultimate use of them is pornographic intent. (ex: I don't find a 2 hour tape of the women on QVC's feet erotic, but someone else surely does.)

What snuff films are not:
• Any video of someone being killed (by any means). These aren't all that rare, and instead fall into the mondo category.
• Someone's personal collection of video murders that they commited. They were not intended to be sold, so therefore are not snuff.

Some snuff film facts:

The first movie to work of the snuff myth was in fact called "Snuff". It was actually an Argentinian film called "The Slaughter" that was bought by a B movie producer named Allen Shackleton. Allen re-edited the film and re-shot the ending. He then hired a few policemen to plant stories in the New York Post and the New York Daily News about snuff films before he released "Snuff". The film did horribly, but it did spawn the creation of the Women Against Pornography group.

In 1990, Charlie Sheen turned over a film called Flower of Flesh and Blood to the FBI, which spawned congressional hearings into snuff films. The porn industry was hard hit by this, and many people testified before congress to say that snuff films just don't exist.

Al Goldstein put up a reward of one million dollars for anyone who can produce a real snuff film. He put up the reward during the previously mentioned congressional hearings to show just how silly they were.

It's rumored that David Berkowitz (or accomplice) filmed the murder of Stacy Moskowitz for Roy Radin, a showbiz entrepreneur and porn collector. The murder was supposedly filmed from a van across the street, but the van was never mentioned in any police reports.

While the FBI continues to say that they have never found a true snuff film, various sources (doctors, policemen, and a few convicted pedophiles) say they have seen them.

There is a book called Gods of Death by Yaron Svoray in which he travels the globe in an attempt to find a snuff film. In the book, he attempts to buy various films, and witnesses the showing of two. It's not known whether the book is fiction or fact. The stories are overdramatized and it's up to the reader if it's true or not, as the author has never commented on it. Personally, I think it's total crap. He ends up getting a video from a Serbian soldier turned porn director, but then loses it on the way home? Seriously, it's just a scare novel.

There is a Reuters news story involving an Italian child porn ring being busted. The ring sold videos ranging in price from $400 - $600 dollars. The most expensive of the videos were called "Necro Pedo", and supposedly involved the rape and murder of children. I have seen this article only twice, and the snuff films are mentioned only in passing. I don't know if they actually found the videos, or just found the description from the web site the group was selling the video from.

Also in April of 1999 two German men, Ernst Dieter Korzen and Stefan Michael Mahn, videotaped themselves raping and torturing a 21 year old prostitute. However, the prostitute died before they could finish the video and they went out to kidnap a second victim. She escaped and notified authorities who quickly arrested the two men. The men testified they planned to sell the video in America for $16,000, where they said there is a large audience for such violent video. Both men were sentenced to life in prison. The chief prosecutor, Wolfgang Rahmer, stated that he had no doubt that an industry for snuff films existed.

Serial Killers and Video
(October 23, 2001) Since the original submission of this node, many people have /msged me to comment or ask about video tapes made by serial killers. I would like to note that none of these videos contain the actual murder usually just the victims before the actual murder. So, these are not snuff films, but they deserve mention in this node.

Charles Ng videotaped several of his victims, sometimes through a one way mirror othertimes while standing within the room the victims were held. The videos were used in their prosecution and showed two of their victims: Brenda O'Connor and Kathleen Allen.

Paul Bernardo and Karla Homolka videotaped the bondage and sexual torture of two of their victims: fourteen year old Leslie Mahaffy and fifteen year old Kristen French. The video depicts rape, bondage, and Bernardo urinating and defacating on them. The videos were shown to the jury during their trial, but only the audio portion of the video was played for those in attendance. The videos have since been destroyed, but rumours persist that a second set had been stashed away by Homolka)

Lawrence Bittaker and Roy Norris together kidnapped and killed fifteen teenage girls. Before killing their final victim, Shirley Ledford, the pair made an audio recording them raping, sodomizing, and torturing her.

Are snuff films a myth? I think they are, but if they do exist they certainly won't ever make it into the public. They would be rare, very expensive, and certainly wouldn't be copied. Yaron Svoray does say he attented a very small showing of a snuff film for $1,500. The owner of the film stayed in the room, and brought his own equipment to make sure nobody copied it. Many people feel snuff films "just have to" exist and law enforcement agencies continue to investigate.

Another note: Probably the closest commercially available videos that are close to snuff are called "Squish Video" or "crush video". These videos involve someone (usually a woman) crushing small animals to death with their bare feet or high heels.

Reuters story: http://www.newsfactor.com/perl/story/4680.html
Thanks to Timeshredder for corrected information on the Bernardo/Homolka trial.