Occult for Fun and Profit!

I had a roommate once at an art school in California over the summer who called himself Cockroach.  No, it's not just a borrowed cliche, he actually had a giant white cockroach painted on the back of his full length black leather trenchcoat which he wore religiously in the middle of 114 degree Southern California weather.  He had long black hair, white, white skin, and pale purple glasses.  He even wore his fingernails long and manicured to fine points.  His art was dark and Cravenesque, a 3-dimensional fleshless face in a box, an oversized portrait of a sinister vampire, three skeletons relaxing around a campfire in a cavern of vascular flesh....well, you get the idea.  I asked him once wether he thought he was a vampire. 
His response: Of course not.  Vampires don't exist.  I'm a witch.

I have since met many people who purport to being involved in one way or another with Wicca, witchcraft, or the occult, not to group the three together too ignorantly.  My point, or the idea that I am trying to come to, is that there is a similar response among the practitioners when asked about the validity of their art to that of the many sects of Christianity.  That is, "the way I do it is right, everyone else is wrong." 

For myself, I like to believe that true Wicca is gentle.  Earth loving, pagan in origin, and more about healing and worship of the natural world and its wonders.  But I do know that there are groups who delve into what seems to the earth children as deeply misguided dark arts. 

These are the practices and rituals that, for my current purposes (research, writing, character study, etc...not to put a hex on the guy who yelled at my wife like a jackass over a damn babyruth candybar...although...) I want to know from you all, what are some practices you've heard of?  Perhaps witnessed or read about.  Any sources you have seen and trust, or even if you have participated.  The stranger the better, as long as its real or believed to be real. 

What do you know?