My pick is from the film Love Story- “Love means never having to say you’re sorry.”
In one of the Chuck Norris movies (can’t remember which, dammit), a female lead is frantic because she has to leave her apartment after a gruesome crime has been committed, and repeatedly exclaims “I must have my things!”.
Dr Flexi Jerkoff in Flesh Gordon, after opening the hatch to his spaceship on an alien planet:
“Good, there’s oxygen here.”
Astronaut Nick Adams, speaking to aliens in Monster Zero:
“What have you done with our spaceship?”
Do Ed Wood movies count as “art”?
Multiple Oscar-winner Sir Anthony Hopkins was stuck saying this in Mission Impossible 2:
To go to bed with a man and lie to him? She’s a woman - she’s got all the training she needs.
From Plan 9 from Outer Space:
“Can you see or measure an atom? Yet you can explode one. A ray of sunlight is made up of many atoms!”
Lots of good lines in this one! 
Both are not only fine but likely to be rich veins of ramped-up awfulness.
I caused a foofaraw last year with this:
The Rage: Carrie 2 has a line that just doesn’t sound right to my ears. The “high schoolers” (most in their late 20s) are at a party at someone’s house when they piss off the girl with the telekinetic powers who proceeds to kill them all in gory fashion. Trying to discover who is causing the fracas, one of the dolts proclaims, “IT’S HER! IT’S HER DOING IT!” I don’t expect the King’s English, but Jeez!
If your objection is the use of the objective pronoun as a predicate nominative, it doesn’t particularly bother me. It’s not grammatically correct, but I find it far less jarring than the all-too-common use of subjective pronouns as (usually compound) objects.
Sorry, you lost me at “objection.”
“It’s her! It’s her,” sounds OK. “It’s her! She’s doing it!” Also fine. “It’s her doing,” sounds too Sherlock Holmes-ish.
When I was 16, I watched a deservedly long forgotten movie called “Tuareg” in a theater with my best friend Frank. Of course the well-traveled protagonist Tuareg falls in love at one time in the movie, and his girlfriend asks him “Tell me about the ocean. What’s it like?”. I immediately blurted out “It’s a desert of water”, and you guessed it, that’s exactly what he answered. Frank cried out “How did you know that?”, and I said “Come on, that was sooo obvious.” And that’s why I remember that terrible line from a forgettable movie.
I think it was this:
In the legal trade this is called “A statement contrary to interest”. 
As in “Congratulations! You’ve just nominated yourself as the next gory victim.”
I’m not going to tell you what happens to Amy “Sue Snell” Irving. Yes, Amy Irving! Not worth your time to find out.
From Plan 9 From Outer Space
My friend, you have seen this incident based on sworn testimony. Can you prove that it didn’t happen? Perhaps on your way home someone will pass you in the dark, and you will never know it, for they will be from outer space.
From Alice in Wonderland: An X-Rated Musical Fantasy
May my rod and staff comfort thee.
Sometimes the awfulness is intentional. One of the Life in Hell cartoons has something like “…from the lowly sea slug to our most eminent, brainy science guys.” It’s not dialogue, of course, and that’s fine for this thread.
Or maybe in a work about a poorly written play. Films like Bullets Over Broadway or The Producers must have a few howlers.
I always cringed at Roy Batty’s line in Blade Runner before he killed his maker, Tyrell. “I want more life, fucker.” It came out of nowhere in a movie where up to that point really didn’t have any profanity so it seemed very out of place. In Ridley Scott’s ‘final cut’ version of the film I’m really glad he chose to change it to “I want more life, father” where it really resonated and made it personal with Tyrell. You’re not just my maker scraping a project, you’re my father killing his son.
Maybe not fair as it’s from a movie aimed at kids, but still–
From The Voyage of the Dawn Treader, the third (and last) of the relatively recent Narnia movies:
Young female character, invented for the purposes of the movie, to Lucy: When I grow up I want to be just like you!
Lucy: No, when you grow up I want you to be just like you!
Gaaaah.
From Willow…
Willow: “You really ARE a great swordsman!”
I suppose there’s nothing wrong with the way the line is written, but it is delivered in the most unnatural, over-the-top manner. It’s either hilarious or cringeworthy…depending on how much I’ve had to drink and whether I’m watching it by myself.
Yeah, I entirely agree.
The story was that, as needed, some scenes were shot twice, with a sanitized version to be used for TV screenings. The mystery is, at some point in the finalization of the movie for theatrical release, a creative type* must have looked at the two versions of the scene side by side and said to themselves: “You know what, we’ll go with Fucker.” Sheesh.
j
* - presumably not Ridley Scott, as he authorized the change to Father for the Director’s Cut and Final Cut.
