The killer ripping the pregnant woman's fetus out. It was so realistic that in Britain it was thought that the scene was genuine and it consequently got itself banned. (It was not genuine; the fetus was a rabbit carcass.)
At the end, the recently disemboweled killer starts eating his own spilled innards as he dies.
In a flashback/dream sequence in Audition, one of Asami's previous boyfriends is shown. He is missing both feet at the ankles, both hands, his eyes, and his tongue. Asami vomits into a bowl and offers it to him, and he drinks it hungrily.
The climactic scene near the very end of Fight Club, where the protagonist blows a hole in the side of his own face in order to kill Tyler Durden.
The Canadian sci-fi/horror trilogy Cube definitely has this, with lots of scenes involving people being subjected to various deadly traps including sprays of flesh-melting acid and people-slicing wires.
Austin: This coffee smells like shit! Basil: Austin, it is shit. Austin: Oh good, then it's not just me. Austin drinks the "coffee" while Basil looks away, disgusted. Austin: It's a bit nutty.
The scene in the third movie where Goldmember eats a flake of his own dried skin and describes it as salty falls under this.
In a flashback in Bloodbath at the House of Death, Dr Lukas Mandeville's monocle falls into an incision in the patient on whom he is operating. He gropes around in the incision in an attempt to retrieve his monocle, but he only succeeds in pulling out handfuls of flesh and organs.
The obscure, low-budget Australian comedy-horror film Body Melt (said to be Tarantino's favorite Australian film).
Among its bits of nastiness: A man drinks a bottle of detergent and tentacles grow out of holes in his neck and extend up his nose, the face around a man's mouth splits open and he grows ears in the palms of his hands, a pregnant woman's chest swells up and explodes and her placenta shoots out of her vagina and attacks her husband, a man's penis grows and explodes, a man drowns in his own snot and mucus whilst coughing and sneezing, a child cracks their face open whilst skateboarding, a woman's head shrinks and dissolves into mucus, and a woman's tongue grows until she can't breathe and chokes.
Tarantino was a talking head in Not Quite Hollywood, a documentary of Australian films, and he clearly had a lot of enthusiasm for the subject, mainly because of their over-the-top recklessness. For him to call this his favorite is saying a lot.
In the very first scene, Michael Gambon's character is punishing the cook. He strips him naked, issues a savage beating, and then as a final degradation forces him to roll around in dog feces.
At the end, Helen Mirren serves her lover's dead body to her husband as a meal, after the husband had ordered his brutal death. At gunpoint, forces him to eat it. While her husband is gagging down the meal, she shoots him.
And Crash. If the fact that it's about a secret society of people with a sexual fetish for car crashes whom deliberately crash cars and have sex in the wrecks wasn't enough, it also contains a scene where a man has sex with a woman via a wound in her leg that resembles a vagina.
The Brood. A woman chews through an amniotic sack growing directly out of her chest, takes the fetus out and licks it clean.
The chicken. And the baby; specifically when he cuts it open.
The sperm-like creatures crawling all over the apartment. Not so gross, until you find out that Lynch used real human umbilical cords.
Event Horizon. The infamous video log left by the last crew because hyperspace was indeed a scary place and made them do very, very icky things to one another, including one crew member trying to reach down his own throat and pull out some thankfully-unrecognizable organ.
Evolution. An alien dragonfly burrows under a man's skin (à la The Mummy) and is removed via having a set of forceps stuck up his anus. Later, that same man gets sucked up into the anus of a giant amoeba.
The German indie/DIY production Olaf Ittenbachs Familienradgeber 1&2 (Yes, it's spelled with a 'd') exists solely to play this up to eleven. There is also a lot of Black Comedy involved, more often than not literally. One scene in the sequel shows the protagonist/director pooping in his underpants while brushing his teeth, then scratching his soiled butt with the electric toothbrush, then sitting down still in the same underpants and drinking his breakfast beer and finally dropping them in his sleeping wife's face. Also, guess what the meat loaf in the first part is actually made of.
The Feast trilogy, especially in the second when the dead creature sprays semen over everyone and they begin to vomit uncontrollably.
Freddy Got Fingered. Tom Green masturbates a horse, masturbates an elephant, skins a deer he ran down with his car and dances around wearing its bloody carcass, licks the open wound of his character's best friend, and sticks his hand up a pregnant woman's vagina to rip the baby out and then swings the baby around his head like a lasso by its umbilical cord.
Ghost Ship. Two men eat some seemingly innocuous tins of beans and rice from the kitchen of a derelict, adrift, haunted ocean liner. Then they realize that they're actually wolfing down... maggots.
The early-80s horror movie Happy Birthday to Me has an extended brain surgery sequence. The filmmakers wanted to ensure it was realistic, so they hired an actual brain surgeon to play the brain surgeon.
Hostel. The most disgusting moment in the film is easily the bit where Paxton cuts the optic nerve of the captured Japanese girl, who has had half her face burned off.
The sequel takes this Up to Eleven: In the 1st film there were 3 people involved in the centipede, in the sequel there are 12 people. Also, a woman gives birth inside a car and actually squashes the newborn's head to escape in the car from the villian.
Gozu, by the same Takashi Miike who brought you Audition. The Yakuza boss with a fetish for having cookware inserted into a non-culinary orifice is particularly revolting.
Lost Highway itself has numerous instances. The one that's probably the most disturbing flashes by extremely quickly: a security camera image of him with Renee's body. She is dissembled, with her lower body positioned to mimic the Black Dahlia murder, and Fred is grinning at the camera. This adds Squick to another apparently innocent security camera image, which shows Fred and Renee in bed together. But Renee appears to have seams on her limbs, suggesting that this is actually Renee's reassembled body.
In order to make room for his massive meal at a fancy restaurant, Mr. Creosote projectile vomits, repeatedly and realistically, onto the floor, into a bucket, and all over the wait staff. The other customers are so disgusted by this that they too begin to lose their dinners — no doubt channeling the reactions of the audience. This culminates in him exploding and spewing his innards and the last bit of vomit all over the restaurant. Worth noting that Quentin Tarantino, the gore-master himself, finds this scene to be too much to stomach.
One poor extra, in fact, was apparently so overcome by the stench of the mixture used for the vomiting/explosion that he threw up for real. If you watch the right-hand side of the screen in the closing shot, the poor guy is painfully obvious...
It's about atrocities in the form of grotesque human experiments conducted by Imperial Japan's Unit 731 during World War II to try making biological weapons. It contains a woman's arms being frozen and then the flesh being ripped off them exposing the bones whilst she is still alive and screaming, genuine footage of the autopsy of a child, a cat being thrown into a room of rats to be devoured (which may or may not be unsimulated), and; and this one's the kicker; a man being put in a pressure chamber and the pressure then being raised until his intestines squirt out his anus.
The child was still alive and awake during the autopsy.
Any scene involving scarabs. Especially the one where a scarab crawls out of Imhotep's neck and into his mouth and he eats it.
What about that one scene in the second movie where past-Imhotep and Anak-sunamon are kissing, then the scene shifts to the present-day (in the film), and she's kissing a decaying corpse.
Oldboy : Oh Dae-su eats an octopus alive. Its tentacles continue to twitch and slither after he bit the head. It's a real octopus, by the way.
This pales in comparison to the actual plot wherein the main character is tricked into falling in love and having sex with his own estranged daughter. His tormentor later coerces him into severing his own tongue.
Braindead has several moments, and reportedly got so bad at times that movie theaters actually started offering free barf bags to customers.
Meet the Feebles: an antropomorphic fly character landing on a pile of feces in toilet bown and feasting on it in extended close-ups. A rabbit character slowly decaying from a veneral disease as his body gets covered with boils. The fact that they are puppets may have averted murders and disemboweling scenes somewhat, but there are a lot of other nauseating things that look realistic enough.
Oh, so very much from Problem Child 2! Junior peeing in a pitcher and watching with glee as someone drinks it, believing it to be lemonade. A small dog that drops feces twice the size of himself. Junior loudly farting in the principal's office. The food fight, with pizza that looks disgusting. Cockroaches infesting a family meal. And then, the vomiting scene! Dear god, the vomiting scene! Junior turns a ride at a carnival up to full speed, causing all the riders to vomit, which in turns causes people watching to vomit, which causes more people nearby to vomit, etc.
The scene where decomposing pig corpses were fed into the grinder and the resulting goo was used to drown a victim.
Amanda being thrown into the pit of dirty syringes.
Not necessarily a trap, but the opening scene of Saw IV involving John Kramer/Jigsaw's autopsy was pretty gruesome.
And then there was that scene in Saw 3D – which topped the rest of the franchise in terms of [[gorn]] already anyway – in which the protagonist attempts to free an unlucky victim by trying to retrieve a key hanging on a fish hook inside the victim's stomach. It doesn't help that he has to muffle the victim's screams while slowly pulling on the string tied to the hook, since the trap is connected to a sound meter, which in turn makes the whole scene excruciatingly long. It also doesn't help that, once he gets the hook out, apart from the key, there's also lump a lump of flesh on it...
When Dave is dragged though the window of the Winchester, and his stomach is ripped open, while the zombies outside tear out his insides and he is still alive and screaming as his stomach is being ripped open?
Squirm is about killer worms, and how they get under their victims' skins, literally.
The sound effect used in Stir of Echoes for a fingernail snapping off that is stomach-turning. Apparently the visceral reaction the sound inspired in the audiences took the filmmakers by surprise.
Strange Brew: After Bob and Doug drink all the beer, they try to take their dog Hosehead's bowl, which has beer in it, by giving the dog a donut, and then they pour the dog's beer into another glass for their dad.
The scene in Thinner where the guy slices his hand open and pours his blood into a pie.
The scene where the curly-haired kid projectile-vomits blood in Trick 'r Treat.
Tropic Thunder, the scene where Ben Stiller's character tries to prove that the director's death was fake... by tasting the bloody tatters still attached to his head. Even his co-stars are revolted.
The vampire dinner scene in Waxwork has vampires loudly slurping up bloody chunks of meat. And another scene where China finds her "fiancé" on a slab, still alive, with the meat cut off of his leg, leaving just muscle and bone. It doesn't help that a vampire falls on it later on, causing it make a disgusting breaking noise.
Repo! The Genetic Opera: Two people are disemboweled with no anesthetic, a man has his spine removed and a girl's face falls off.
In the second Urban Legend, when the main character finds the corpses of her friends, there's a graphic shot of rats eating their way in and out of one of the bodies.
Jan Svankmajer's Food has a final part called 'Dinner'. This involves a man covering his own severed left hand in condiments, then eating it after nailing a fork to his new, wooden hand, followed by an athlete eating his own left leg, a woman covering her severed breasts in lemon juice, and finally, the clincher, a slobbish, hairy fat man sticking a fork and knife in his own genitals, before covering them and shooing the audience away with his hand. Especially disgusting if you're having sausages for dinner that night.
Year One had some very gross scenes, like Jack Black eating poop, Michael Cera (the Butt Monkey of the movie) having a Potty Failure resulting in him peeing all over his face, and Michael Cera rubbing oil on Oliver Platt's chest.
Duncan drinking dog pee to cleanse himself after diving his hand into a crap-filled toilet in a gentleman's club to retrieve a ring that was recently peed out by a stripper in Mystery Team.
Andre the Butcher: The title character eats his own scabs.
In Marley and Me, the dog swallows a ring, so later the man has to hose the dog poop down and retrieve the ring out of it. We see the dog poop close-up, and see tiny chunks of corn in it too.
Turistas has a scene of a woman being vivisected on-screen, because the doctor believes that organ theft from the poor is how the rich foreigners take advantage of Brazilian "natural resources" and delivers a Breaking Speech about "collecting payment" to her tied-up boyfriend while slowly and methodically extracting her organs one by one. She's fully conscious while it happens, crying and whimpering as she watches the doctor casually pulling out a kidney through the incision on her belly. After everything of value is removed, her topless and still bleeding corpse is dumped into a sideroom for the boyfriend's rescuer to stumble on.
MouseHunt, while more goofy and family friendly, has one scene where a character accidentally eats half of a cockroach that had fallen into his soup. He stares in horror at the still twitching other half of the roach before dropping it, then it scurries away.
It is established in Jack the Giant Slayer that the giants are fairly disgusting creatures, scratching their butts, along with several fart and belching jokes sprinkled throughout. One is also shown picking its nose...and then eating the booger he picks out. Mind you this giant is the chef.