These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The Domestic Abuse storyline. A full year after it started, it appeared to have reached it's conclusion - only for the Kirsty to find out Tyrone was planning to leave her immediately after they got married so he could get parental rights to his daughter. Kirsty then fell down the stairs after Tyrone moved out of the way of her attempted strike and accused him of abusing her.
Tracy Barlow's obsession with Steve Macdonald. Even Kate Ford, who plays Tracy, is sick of it at this point.
Celebrity Paradox: Nobody ever watches TV; Nobody in the street seems to have noticed a sudden infestation of meerkats, a species native to South Africa, and are asking whether this merits intervention by the zoo, the RSPCA, or Rentokil (An insurance company using anthropomorphic meerkats as mascots is "sponsoring" the show, with commercials at the start and finish of each segment.These feature the lovable animals drinking in the Rovers, dining in Roy's café, and doing other cute meerkat things.
Creator's Pet: Sean Tully. Especially if you happen to be gay ...
Ensemble Darkhorse: Richard Hillman is still fondly remembered as one of the greatest TV villains of all time, and it's more than a decade since he died trying to drown his family.
Kevin Webster (during the War of the Websters storyline). His wife Sally was a borderline example too, though she at least got several Take That, Scrappy! moments.
Marty Stu: Although he has always been seen as Gail's pride and joy, he has horrendously backslid into this since being portrayed by Ben Price.
Memetic Mutation: Granted, it was before the internet became as prominent, but the "Free The Weatherfield One" campaigns that sprung up across the UK after Deirdre Rachid (presently Barlow) was falsely imprisoned.
Ascended Meme: You know a storylines successful, when the Prime Minister of the time comments about it in Parliament.
Rescued from the Scrappy Heap: Inverted. Michelle Connor was actually quite popular when introduced. However as she dominated more and more storylines (and they got really weird), fans grew sick of her and despised her.
The Scrappy: Janice Battersby. There have been many more over the years, but most are either Rescued from the Scrappy Heap or written out, whereas Janice has remained for years despite the fan's dislike.
Kevin got very unlikeable too in recent storylines.
This is of course a regular trope, but a particularly memorable occasion was a 80s scene of fan favourite Hilda Ogden opening a parcel containing her recently deceased husband (and fellow fan favourite) Stan's glasses, and her subsequent breakdown into tears.
The Fiftieth Anniversary. Explosion, train crash, deaths, war flashbacks, fires, injuries.
John Stape's death.
Hayley Cropper's death. Oh dear GOD.
True Art Is Incomprehensible: Played with in an episode. Toyah Battersby, an art student, tries to pass off her slovenly step-father Les' chair, covered in debris such as empty beer cans and old cigarette stubs, as her art project to her tutor. He tells her about an occasion where he had a student who tried to pass off a pile of bricks as his art project, which the tutor didn't buy, and he failed him. He then asks Toyah to explain how her "project" is anything other than a ratty chair covered in rubbish. She improvises a pretentious explanation about how it represents the British working class, which the tutor doesn't buy, until he sees Les for himself, and agrees it is an accurate representation of him, which causes him to not only give her a high grade, but also recommend her project for an exhibit. Its particularly funny because Toyah literally threw the whole thing together at the last minute using the first things that came to hand, because she had neglected her project until only moments before the tutor turned up at her house.