You know what really grinds my gears?: The moaning thread.

[Tonus]

Well I don't know exactly what movies you mean, but I am easily terrified so I'm sure I'd think they're scary.

Probably the "found footage" genre, which was popularized (if not started) by The Blair Witch Project. It's been done so many times in so many genres now that the flaws and cliches are what stand out more than anything. The Paranormal Activity franchise has used it through five or six films. I've seen the first four, and they quickly progress from a pretty good idea that is presented fairly effectively to a tired routine that you already saw in the previous films. The first three have an overarching narrative that becomes more interesting than anything that actually happens in the films. But the scares become predictable after awhile.

It's been particularly abused in the "film crew visits a haunted location to debunk ghost story" movies. Those in particular tend to overuse the trick where the camera is focused on a location where everything is normal, pans to one side to find nothing, then pans back to the original location and there is some ghost or creep just feet away. It's a variation on the ploy where a character gets a fake scare ("it was just the cat") and then turns around to find herself face-to-face with the demonic killer. It might make you jump, but after a while it is more annoying than scary, and pulls you right out of the viewing experience.