Tech Infantry, as a spinoff of the Old World of Darkness (see above under Tabletop Games), also has the Tszimisce clan, but their Viscissitude abilities are weaponized for soldiers of the Black Hand. These abilities are also retconned into being partial but progressive possession by the Soul Eater aliens from the planet Fieras VI, who eventually transform their victims into new Soul Eaters and completely take over their minds.
Amusing fact: This isn't actually a retcon as such, because the origin story of Vicissitude as given in the much-reviled supplement Dirty Secrets of the Black Hand is this, except replace "alien virus" with "spirit virus from the netherworld." That idea was retconned in revised edition, so Tech Infantry is retconning the Retcon.
In New Vindicators most of the superhumans are fairly normal looking, with the occasional ape person, or winged girl, but that can sometimes be a good thing. Even ancient Nephilim like Apocatastasis, who's freakishly tall and has twelve fingers, aren't that bad. But Bulwark actually has it fairly bad-he's a rock man, like the Thing, only played a little more straight. So no eyes, no functional nose, no sense of touch-'seeing' through vibrational senses, he's a mutant freak among mutant freaks.
The SCP Foundation has so very much that trying to list them all would involve recreating half the site here. Reading random articles for any length of time is bound to make your skin crawl.
Virtually any SCP labelled "transfiguration" will involve some degree of this trope.
SCP-212 ("The Improver"). This device performs bizarre surgical procedures on its victims that leave them worse for wear. Changes have included replacing teeth with sharp blades, replacing feet with pads, and replacing hands with tentacles or crab claws.
SCP-1707 ("New Skin"). Having your skin removed and replaced by a colony of worms can ruin your whole day.
Parodied in Homestar Runner: An Easter Egg in one of the Halloween specials shows the character Stinkoman (a character who is a walking anime parody) dressed up as Speed Racer for Halloween, and he comes up to 'your house' to get candy. One of the treats you can give him is a can with the word "Akira" printed on it. Guess what happens when you give that "Treat" to Stinkoman?
"Waaaaaaagh!! ....It tickles!"
Gaia Online's Timmy experienced this trope in an Ugly Cute way after his legal guardian sealed him in a barrel of toxic waste just to see what would happen.
It says something that even Timmy is grossed out by the Penanggalan from the Nightmare evolving item. "It even has a cute female companion— eeeeeugh never mind I think I have to go lie down..."
Which is sad because the Penanggalan is really quite Moe... at least, as much as a severed head with a dangling string of entrails can be considered Moe.
There is a well circulated picture called Lotus Boob. The image of a lotus superimposed over a human areola and its implications of burrowed parasites is more than enough horror. Thank God that it's fake.
In the same vein as the above example, there's a email on Snopes with a .jpg attached of human fingers with lamprey mouths Photoshopped onto the pads. It's meant to be a joke: too much typing and mousing will wear holes in your fingers, har har!
The infamous Goatse while we're at it. How is that physically possible.
Encyclopedia Dramatica uses it on the 'kittens' page.
Whateley Universe. Horror author Michael Waite is dying of cancer. Oh no, that's just what the doctors think. It's much worse than that. After he 'dies', he wakes up in the morgue. For starters, he vomits up his own internal organs. It turns out the reason he was such a good horror story writer is he's not fully human to start with.
Every single character in Ruby Quest. (Minus Bella, that is) Some of them aren't particularly obvious — Red, for instance, looks perfectly normal in his first appearance. And then he laughs. Others, though, are so twisted you can barely tell what they once were, including Stiches and Number Six. Oh dear god, Number Six...
If you can actually guess where that's going, by knowing something about bagworm moths, you're probably wearing a body suit made of people.
Hey kids, did you ever wonder what's the REAL reason why you put different Pokèmon into different Pokèballs? Well, wonder no more.
Many of the "powers" in Survival of the Fittest Mini site spinoff SOTF: Evolution fall into this. Some are pretty "standard" as powers go, such as solar-poweredSuper Strength and invisibility, "memory absorption", Telepathy, and control over electricity, while others are pretty pathetic. Others, however, include things such as mold growing from the mouth and a character developing cat-like claws that are poisonous. The most notable one, though, goes to Johnny Marsh's "power", in which his skin is invisible, but the rest of him (muscles, organs, etc.) aren't. This means that his muscles are completely visible like an anatomical model. This receives a Lampshade Hanging when the scientists puts a full-body scuba suit on him to avoid him scaring the other subjects and interfering with the research. And then there's Billy-Jay Clarke's death in which he suffers a power malfunction, causing his eyes to catch fire and melt out of their sockets...
Worm: Mannequin of the Slaughterhouse Nine turned himself into a puppet-like monstrosity whose internal organs are all housed in seperate transparent cases, all attached to a long-limbed body with ball joints at every joint.
Bonesaw, also of the Slaughterhouse Nine, as a tinker who specializes in organic bodies, might as well be a Body HorrorFactory.
This, other than death, it causes your blood to turn to crystal and go through the skin. According to the story, albeit vaguely, it seemed to come in variation but in the most extreme cases the person is already dead and barely recognizable.
The works of Karl Persson are a little like what you'd get if you combined the brains of H. R. Giger and Sigmund Freud, and soaked the result in a bucket of liquid LSD.
In the the The Salvation War, while Angels (like demons and "second Life" humans) have a healing factor. The angels sent to Michel's concentration camp find out horribly that growing back does not mean growing right. The Angels who were nuked suddenly were less "angel" and more "Angel shaped cancer tumors".
In The Wanderers Library story Abundance, a stranger feeds a starving village by causing select villagers to grow new limbs and other meaty appendages, which they then cut off and eat.
Killer Monster describing how he tortures his victims in 'The Camping Webisode' of DSBT InsaniT.
The Cartoon Man parodies typical Body Horror scenarios. Instead of some kind of horrific monster, Roy turns into a hyperactive cartoon character with giant eyes and White Gloves. It's still rather horrifying for everyone involved.
From the twisted mind of Eyesglowyellow comes the Metokur chimera who — in the first two stories it appears in — turns the main character's head into a penis and another character into duct tape.
In The Saints, corruptedghosts are often heavily disfigured, either from Self Harm or from other corrupted ghosts. Thorolf, the one corrupting the ghosts, is very decayed, with most of his skin rotting away.
Kalia's One-Winged Angel form in Dreamscape where 8 long arms with golf club-shaped hands come out of her back, as well as two smaller legs come out of the sides of her knees!