The horror movie that I am thinking of right now is “The Bride of Chucky” and when I saw that in the theatre everyone laughed especially when Chucky’s girlfriend says as they are getting ready to have sex “Aren’t you going to use a rubber?” and Chucy replies “I’m all rubber”.
I didn’t get around to seeing *The Exorcist * until 1979 or so. Watched it. Wondered what all the fuss was about. Finally, she vomited pea soup all over the priest. I burst out laughing, and kept giggling for most of the rest of the movie.
It just keeps getting funnier, every time I see it…
Shocker- I saw it Halloween night the year it opened. Laughed at the terrible plot twists.
Blair Witch Project. Hideously awful film.
The Amityville Horror.
“IT’S THE GATES OF HELLLLLL!!!”
When I was a student, there was a horror film festival on campus one year in honor of Halloween. I saw Carrie for the first time, and laughed at many parts, including the first sight of the male lead’s hairstyle! But setting aside dated fashions and intentional comedy relief (that was the purpose of the otherwise pointless “shopping for a tux” scene, right?), I laughed really hard at the end when…
Carrie’s hand comes out of the ashes of her burned house and grabs the other girl.
The rest of the theater screamed then laughed, but I saw it coming and just laughed. 
Pepper Mill and I laughed and groaned at the end of The Ring when the girl came out of the TV. It was just so thoroughly ludicrous (and the idea has been played, in a lot of movies and TV shows, for laughs for many years.)
I keep thinking – what if they had one of those min-TVs? Would she have come out the size of a mouse? 9Then looked around in bewilderment as the artist guy stepped on her). And at the beginning she’s supposed to have killed a carful of kids. Did they have a TV in the car?
And what if you’re nowhere near a telephone after you watch the tape? Do you… ahhh, forget it.
The Exorcist the first time I saw it. For me, it was the exorcism scene–while the priests are performing the ritual, there’s a sort of silhouetty profile shot of Linda Blair writhing on the bed with her tounge hanging out. I started to laugh, and went on either laughing or trying not to right up until Father Damien made his dramatic exit.
Freddy vs. Jason, Halloween: Resurrection, Signs (if you wanna count the latter as a horror movie, of course).
The “original” Dawn of the Dead. When I saw the zombies eating pizza-ish skin/guts from their victims I laughed at the piss-poor effects.
I stopped laughing when I realized I had layed out my hard earned money to sit through that dreck!
Freddy 1 (?) when Johnny Depp gets sucked into the waterbed, then blood gushes everywhere. In the next shot, the detective finds poor Johnny looking out of the waterbed bag. Funny stuff.
Glad to see Johnny’s gone on to better things, much as I love Freddy.
Snicks
In Near Dark (one of the greates vampire movies ever, in part because they don’t actually say the word “vampire” any time during the movie…), Lance Hendrickson is the leader of the vampires. A mortal shoots him in the chest, Lance looks down, coughs up the bullet, and tucks it into the mortal’s shirt pocket. Heh.
The Zuni Devil Doll segment of Trilogy of Terror—I was 18, I think, when it first aired, and I fell off the sofa laughing at regular intervals.
Evil Dead II
“Now you listen to me… You hear what I’m saying?.. I’m alright!!” - Ash
I laughed hysterically at the new Dawn of the Dead… but I still thought it was a great movie.
Brotherhood of the Wolf isn’t sure whether to be a horror movie, a fantasy movie, or an action movie, but it’s close enough to qualify as horror. And I was about the only person in the theater to burst out laughing at one particular scene.
I’m just a sweet transvestite…
Daniel
Jack Frost. Not the Michael Keaton one either. There was a horror of the same name which came out a few years earlier. Same premise (guy dies, soul enters a snowman), except this guy was an evil muderer. In one scene, he stabs a girl with an icicle while yelling, “I guess Christmas came early this year!” It was such a terrible line, not to mention terrible film, I had to laugh.
Another vote for Evil Dead 2. The scene where Bruce Campbell fights against his possessed hand is one of the funniest scenes in any movie.
I’ll also put up a vote for The People Under the Stairs.
Wicker Man - Britt Eklund writhes nude in her room, sending a telepathic signal that’s supposed to drive Edward Woodward mad with lust. It’s been 30 years since I’ve seen that movie and remembering that scene still makes me laugh out loud.
Willard (the 1971 version) - It wasn’t so much anything on screen, but the audience started to pick up on what would happen next very early in the movie. By the time Bruce Davison yelled “You made me hate myself!” to Ernest Brognine, the entire theater beat Davison to the punchline and yelled back “But I LIKE myself!”
The Texas Chain Saw Masscare. The second one anyway. I laughed at the poor effects, and how I could predict everything in the movie. And ‘Leatherface’ finds her in the obvious hiding spot in 3…2…1…NOW!