Nedry catches his own intestines. Before losing his head.
The point is: you are alive...when they start to eat you.
Another fun scene: Dr. Wu and the other survivors are holed up in the lodge while Ellie is making a distraction for the raptors so they won't attack Grant, who is trying to restore the park's power. However, two raptors already inside the compound which the survivors had kept in sight suddenly disappear, so Wu goes out to warn Ellie that they are on the move. As he does, one of the same raptors jumps down from the roof, tears him open, and eats him while he is still alive. The attack was so sudden that Wu tried to push the raptor's mouth away from him without noticing his intestines have spilled out of him.
From the first few chapters: "Oh no, we swear he was run over by a backhoe!" And the "Bloody three-toes footprints..."
The bit in the prologue with the guy whispering "Raptor, losa Raptor!". As if that isn't creepy enough, he starts explosively vomiting blood.
Howard King's death in the The Lost World novel. If you thought that just getting your neck snapped was bad enough, King is chased down and torn apart by the raptors and then eaten, all while the main characters helplessly watch on. There's even a graphic description of the raptor chewing through his neck instead of breaking it...
From the first movie. Three words: disembodied, bloody arm.
And let's not forget this lovely gem that precedes it
The scene where the T Rex attacks the car with Lex and Tim inside. Normally you'd expect a car to provide at least a modicum of protection from a wild animal. Not so with the T. Rex.
You think the T-Rex was bad? Think about The Big One for a moment: A hyper intelligent velociraptor that is The Chess Master incarnate. She uses one of her pack members to lure Muldoon out into the open, pops up right next to him, and start tearing him apart a few seconds later. Not to mention the fact that they surprise attacked Grant, Ellie, and the kids and would have killed them had the T-Rex not intervened.
The way Grant describes the way they hunt is pretty unsettling:
Grant: You come across this "six-foot turkey", and you keep still because you think he can only hunt things that move like a T-Rex. He won't see you if you hold still. Uh-uh, not this guy. You stare at him... and he just stares right back. And that's when the attack comes, but not from the front, but from the side. The other two raptors, you didn't even know they were there.
Yeah, I honestly don't get why so many people are more scared of the T-Rex. Sure, she's big and she's tough and has huge teeth, but she's still as dumb as a post. Meanwhile, The Big One could beat you in a game of chess, and then kill you afterwards.
The kitchen scene with the two raptors stalking the children, and one of those raptors being The Big One. Critics didn't name this scene as the 95th scariest movie moment of all time for nothing!
The Dilophosaurus in general. At first it comes across as this curious little critter with a rather cute monkey like cry and you think it's harmless, but then it won't stop coming near you and then HOLYSMOKESWHATISTHAT?!
"Anybody hear that? It's an... It's an impact tremor, that's what it is... I'm fairly alarmed here."
A minor one comes from Hammond himself. Throughout the movie, he's been nothing but a kind, old man who may loose his temper once or twice, but he's the quiet voice of grandfatherly dignity. And then he hears Grant shooting over the phone and screams, "GRANT!" at the top of his lungs. A minor scare, but one of the most unexpected.
From the second movie, to rekindle your fear of velociraptors: the grass scene. You know it, the one where the scared survivors are fleeing from the T. rex in the forest by running through the grass. Particularly that birds-eye shot where they're charging through the grass, being loud, carving a big track and the little trails snaking silently through the grass behind them...
There was a deleted scene where Tembo's friend (the one who shouted to them to stay out of the long grass) realised that outrunning the raptors was futile, and simply opted for a death of quiet dignity, kneeling down as they jumped him.
Arnold dying in that first movie, that scene with Dr. Sattler in the shed trying to turn on the power and suddenly being attacked by a raptor then having Arnold's severed arm fall onto her shoulder.
Eddie's death in The Lost World. He was only trying to help out the gang by pulling them back up from falling off the cliff, but dies after the one T. Rex bites him, carries him up, and shares the other half of him with its mate.
In the Lost World the scene where the heroes are holding off the stalking raptors in the shed. They board up one door to keep one raptor out, only for a second raptor to show up in the same hole that they were digging to get out.
In the Lost World, the scene where the Tyrannosaur shoves its head into the tent where Kelly and Sarah are, sniffing the blood from within the tent.
The Genesis games SEGA screen. It's basically the T. rex sprite (we only ever see one from the shoulders up) in front of a black background with the SEGA logo above him, and he roars "SEGA!!!".
The actual game as Grant. Limited ammo. Dinosaurs at every turn, who 9 times out of 10 want to eat you. Velociraptors who, in addition to being pretty deadly and agile, actually learn from your playing style and can actually duck to avoid your shots. And let's not forget the T. rex, who always appears poking her head out of a hole in the wall and fiercely snaps her jaws in your direction, and can kill you with a single chomp (not to mention she has one of the most impressive dinosaur roars ever made). Her introduction in the Power Station is easily her scariest appearance, as you don't actually see her at first; just some cracks in the wall and a foreboding stomping sound. Get close (which you have to do to exit the level), and CRASH. HUUURAAAAAAAAAAAAAAAR!!!
When you're playing through the Visitor's Center (the last level) as Grant, you come across an elevator. Splattered in blood. Sure, it's pretty tame compared to a lot of today's games, but it's still pretty unsettling, especially since the rest of the game is blood-free. The worst part is that you can only imagine some poor terrified guy trying to escape via the elevator as a raptor closes in on him, only for the elevator to be too slow...
In Rampage Edition, the last level. It starts with Grant on a boat in a river, with nothing else in sight. If you've read the manual, you know the T-Rex is waiting for you. If you haven't... well... you're not going to enjoy what comes next.
Even scarier is the Sega CD version. (Sort of) free roaming, very limited ammo, a time limit (in the form of a plane piloted by a living Nightmare Fuel), and really, very spooky ambiance. Including the ground physically shaking as a T. Rex approaches from god-knows-where for a tasty snack. And it's all in first-person view, so you see exactly what your character is seeing when said T. rex devours him.
The SNES version had First Person parts inside the buildings.. Where random dino growls were to unnerve you even if the rooms were empty! Not to mention that outside that Raptors could jump out from ANYWHERE from bushes and thickets and the T. Rex was an Implacable Dino! Okay, so you're walking around on top of a building (for example, the Visitor's Center). There might be some compies and a dilo or two, but at least you don't have to deal with any rapto-holy fuck they can jump up on the roof!
Again from the SNES version: Don't forget the blackened rooms inside the Visitor's Center/Utility Shed. Unless you have located the night vision goggles, one step inside the room, and some unseen dino swipes at you, killing you and emitting a roar.
The 3DO version is just a minigame collection—nothing scary there, right? Oh wait, there's one game where you're wandering around a nearly pitch-black series of hallways, trying to activate some fuses. You're being chased by Velociraptors; should you run into one, you get a few seconds to contemplate your fate, and then the fucker abruptly flies right into the screen whilst shrieking. Oh yeah, and if that wasn't enough, your character lets out a horrified, blood-curdling scream. Better luck next time...
Jurassic Park III Dino Defender wasn't that bad.... until you die. Then you get treated to a horrifying image of the dinosaur charging you in first-person. THE MUSIC DOES NOT HELP.
In the same game, the level that starts with you being chased by a Tyrannosaurus is terrifying. It's also hard to beat because you can get eaten or fall off bridge!
The 1997 game, The Lost World: Jurassic Park, which allows you to play both as humans and dinosaurs, have a very frightening intro for the Velociraptor section of the game. You are treated to about thirty seconds of footage from the viewpoint of a human being chased, and eventually captured, by raptors. He can't see them, but the players are treated to a graphical interface displaying their location, which shows not only the raptors gradually getting closer, but also more of them being revealed the closer they get. In addition to that, the fleeing human is communicating with someone over radio, and the fear in his voice is very evident. It is very unsettling trying to put yourself in his shoes.
People may have considered Trespasser to be a crap game, and with good reason. But it could pull some genuinely terrifying moments sometimes. Raptors could sneak up on you and kill you from behind. Even if you do see them, the goofy controls meant it was difficult to aim and kill them. Running is often your best bet. And there are also scripted moments, like in level 4's Diner where a dinosaur could spawn in behind you or push open a door. And finally, the T-rex. There is no fighting the T-rex. There is only sneaking by it, or distracting it. Unless you get a good head start, you will not outrun it.
A somewhat obscure, rather mediocre Jurassic Park game called Jurassic Park: Warpath was a fighting game that allowed you to play as several movie and non-movie dinosaurs (including the then-unseen spinosaurus). These being dinosaurs, their attacks could be especially brutal. Among the most brutal were those of the triceratops and styracosaurus, who would impale their enemies during their throw attacks, leaving the enemy dinosaur squirming on the ends of their horns until they were thrown to the ground. Every attack also left some pretty nasty wounds, including some which would do things like leave bones exposed to the open air. Finally, the way to regenerate health would be to catch little running creatures and kill them (carnivores...well, I am sure you can guess. Herbivores would just leave them impaled on a horn and then stomp them to death), but you did not not have to kill them right away. Until you hit an attack button, you could leave a squirming compy, dog orhuman beingin the jaws of a giant carnivore or impaled on the spike of an equally huge herbivore until it was finally swallowed whole or stomped to death.
Even the Lost World arcade game had its moments. Namely, the fight with the Carnotaurus. Imagine, if you will, a dinosaur slightly smaller than a T-Rex that could turn completely invisible out for your blood. The fact that it looks like a giant Jackson's chameleon will either act as Nightmare Retardant or make it even worse.
The most recent game from Telltale Games is full of nightmare fuel, and is perhaps the most horror-themed out of any of the Jurassic Park media. See Jurassic Park The Game for examples.