1. CGI overdesign.
CGI has, in most ways, improved special effects in film--you can just compare SUPERMAN 2 to SPIDERMAN 2 to see that. The thing about CGI is, though, anything's possible, which means it's also possible to make things utterly ridiculous and impractical. That Romulan spaceship in STAR TREK is a good example of something that was ruined by CGI. Basically anything from TRANFORMERS as well.
|"In the future, let's put a lot of pointy things on stuff"
Voiceovers are the screenwriting equivalent of CGI overdesign: something unnecessary that almost always cheapens your film by making things too obvious and unsubtle. Sure there are some voiceovers that work; MY LIFE AS A DOG has a great one, but that's because it's abstract and poetic. Usually, voiceovers serve to simplify complex ideas so marketing executives can sleep easy, knowing their product has been rendered mediocre enough for a mainstream audience. The theatrical release of BLADE RUNNER is the most egregious and infamous example of this.
I can deal with a little comic relief, like R2D2 and C3PO bickering throughout STAR WARS. But as soon as you throw a minstrel-like buffoon on screen, or a little kid who can't act but has an "aw shucks" kind of face, you've lost me. This is a dumb idea that doesn't even work in bad sitcoms. So why put it in your ostensibly serious film? I'm looking at you, 90s/00s iteration George Lucas.
|Wanted for Crimes against Humanity
Ever seen a film where there's a natural endpoint, a place that, if the director decided to roll the credits, would give the film a powerful emotional resonance--and then had to watch that director keep going for another 30 minutes, just so things can be neat and tidy? Steven Spielberg, oh how you wronged me with AI! They were sitting there in that car, and I was ready to be amazed, and then you go and have them rescued by stupid-looking future people/aliens, who then go about making everything happy/obvious that could have been heart-wrenching/ambiguous. Barf!
5. The scrappy kid.
For some unknown reason, the hero befriends some scrappy kid who tends to appear out of nowhere. The hero mentors or chums around with the kid to show that hey, he may be a bad-ass, but there's a beating heart in there, too. Tim Burton's PLANET OF THE APES and TEMPLE OF DOOM stand out as particularly egregious offenders.
|"I am a very scrappy ethnic stereotype"
Some directors have an unmistakable stamp their movies can't help but reflect, and other directors wish they belonged to that group. Alfonso Cuaron found his footing in CHILDREN OF MEN, but HARRY POTTER 3 is chock-a-bock with annoying directorial flourishes that don't accomplish anything, and Gus Van Zandt was kind enough to remind us why Hitchcock was Hitchcock by remaking PSYCHO shot-for-shot and somehow making it clunky and over-directed.
7. The heart-to-heart story.
It's the end of the second act and the hero is down in the dumps. Enter kindly grandma, weird uncle, once-distant parent, whatever, to tell a story from days gone by that utterly encapsulates the hero's current struggle, and what they need to learn from it. See the bar scene in TEAM AMERICA for a wonderful send-up of this, Chuck.
8. The boring, boring worst day.
The lights go down, we're all excited to see what this movie has to offer, only to meet the hero just as they lose their job AND boyfriend/girlfriend on the same day. What bad luck! What lazy writing!
9. Bad accents.
I'm ok with accents that are inaccurate for a time or place, and I'm ok with differing accents across a cast, as long as each person speaks consistently: in their own voice, or with a good, consistent accent. One of my favorite movies - PERFUME: THE STORY OF A MURDERER - is full of different British accents even though it's mostly set in France. All of that's fine by me, but Dustin Hoffman destroyed a really well-crafted film with an awful, awful on-again-off-again Italian accent and the most jarring word stress I've ever heard.
10. Good characters being squandered.
It's so painful seeing characters you love lose most of their depth when they're adapted from book or comic to screen. Why, WHY did they waste Silver Surfer like that?? Other giant disappointments: Cyclops, Phoenix, Rogue, Gambit, Doctor Doom, Venom, Deadpool, and Emma Frost. I'm sure this happens outside the Marvel universe too.
|"I used to be a poetic, tortured soul."
I love a summer blockbuster as much as the next sucker with nothing to do. But I'm pretty sick of the ones that consist entirely of CGI and explosions. I know it's what people want, but I can't even sit through the previews. Seriously -- BATTLESHIP?! I can't believe Tim Riggins agreed to that. See also: TRANSFORMERSES.
12. Awful songs.
It's bad enough if they're in the credits, but it's even worse when they actually make it into the film. Sometimes it's a song you're already sick of (see: Smashmouth's "All Star" in SHREK and then again in SHREK THE THIRD) and sometimes it's somebody new that a label is trying to jumpstart (a lot of songs from most of the Twilight movie soundtracks), but the worst is a new song from a crappy band you already dislike that's trying for a comeback (see: Nickelback in SPIDERMAN, Evanescence in DAREDEVIL, P. Diddy & Jimmy Page in GODZILLA). Giant exception you can feel free to judge me for: MC Hammer's "Addam's Family Groove."