In honor of Halloween, here's a collection of some of the freakiest art out there. Viewer discretion advised!

Bourgeois’s 30-ft spider sculpture outside the Tate Modern in 2007. Photo courtesy the BBC.
What could be scarier than a 30 foot spider? Well, turns out it's actually not that scary at all. "The Spider is an ode to my mother," artist Louise Bourgeois once said. "She was my best friend. Like a spider, my mother was a weaver... Like spiders, my mother was very clever. Spiders are friendly presences... spiders are helpful and protective, just like my mother." The piece at the Tate above was entitled "Maman", french for mother.
Bourgeois has also said of her art: "I turn nasty work into good work. I transform hate into love. That's what makes me tick."

"The Golden Age of Grotesque", (Marilyn Manson), photographs by Gottfried Helnwein, 2003
Gottfried Heinwein's can be absolutely terrifying. What else would you expect from the best man at Marilyn Manson's wedding?
Dealing with images of children, Disney characters, and Holocaust scenes, he uses blood, darkness and sexuality to shock and disturb his viewers. For one of his works, he painted a portrait of Hitler with his own blood. Norman Mailer said of Heinwein:
Well, the world is a haunted house, and Helnwein at times is our tour guide through it. In his work he is willing to take on the sadness, the irony, the ugliness and the beauty. But not all of Gottfried's work is on a canvas. A lot of it is the way he's approached life. And it doesn't take someone knowing him to know that. You take one look at the paintings and you say "this guy has been around." You can't sit in a closet - and create this. This level of work is earned.
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"Piss Christ", photograph by Andres Serrano, 1987
Andres Serrano shocked the art world in 1987 with "Piss Christ", a red-tinged photograph of a crucifix submerged in a glass container of what was purported to be his own urine. Much of his work employs bodily fluids of one sort of another, and his most recent work uses (forgive me!) feces as a medium.
Outside of this grotesque media work, Serrano has shot a vast array of subject matter including portraits of Klansmen, dead bodies in morgues, and burn victims. He went into the New York subways with lights and photographic background paper to portray the bedraggled homeless as art objects, as well as producing some rather tender but sometimes decidedly kinky portraits of couples.

"Myra" by Marcus Harvey, 1995
Marcus Harvey is perhaps best known for his tabloid-provoking 9' x 11' portrait of child murderer Myra Hindley which was created from the handprints of children. The painting had to be temporarily removed from display for repair after it was attacked in two separate incidents on the opening day, in which ink and eggs were thrown at it.
At the time of its exhibition, New York Mayor Rudolph Guiliani called the work "sick and" threatened to cut off public funding to the museum saying "I believe that the use of public funds to have a portrait of a paedophile glorified is disgusting."