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.
Bogs Diamond, the leader of a prison gang called 'the Sisters' who prey on weaker inmates to rape them again and again for as long as they like. Bogs sets his sights on Andy and together with his gang makes repeated attempts to rape and brutalize Andy over the course of several years, succeeding about half the time. When Andy tries to fight off the latest attempt, Bogs threatens to shiv Andy through the skull if he doesn't give him and his buddy oral sex. When Andy talks him out of it by playing on his ignorance, he beats Andy straight into the infirmary for a month instead.
Warden Norton seems like a stern but affable prison bureaucrat before he reveals the true extent of his immorality and corruption. He sets up a scheme to underbid public construction projects with cheap prison labor and pockets the buy-off money from the desperate private contractors he blackmails, using Andy's financial knowledge to launder the illegal money. When a new inmate named Tommy has proof of Andy's innocence, Norton has him shot in the yard by Captain Hadley and the murder passed off as an escape attempt. He throws Andy in solitary confinement for a month, then threatens to destroy everything Andy has built to improve Shawshank over the past 20 years in prison and make sure that he'll be handed over to the rapists again, before giving Andy another month in isolation just to think about it.
Ear Worm: The music that plays when the police are coming to get Captain Hadley and Warden Norton.
Fandom Rivalry: In 2008, a somewhat complicated series of votes on IMDb to give The Dark Knight the spot on the Top 250 as the #1 film of all time (that was from The Godfather) ultimately led to Shawshank topping the list. The Godfather had held that position for quite a long stretch of time, and its fans were, to put it mildly, not impressed; even now, over a year later, a visit to Shawshank's IMDb forums reveals thread after thread attacking it as unworthy of being #1 (and, implicitly or explicitly, favouring The Godfather). This makes the movie inevitably Hilarious in Hindsight when you think about the Robot Chickensketch where... well, you know.
Hadley is played by Clancy Brown, who's best known to Western Animation aficionados as Lex Luthor in various DCAU productions. As of 2011, Mark Rolston, who played Bogs, is now Lex Luthor in a different universe. That's right - this movie features Lex Luthor beating up Lex Luthor.
Captain Hadley had to get some sound financial advice from Andy Dufresne in order to keep a cash windfall intact, the kind of advice that Mr. Krabs would know in his sleep. Krabs certainly wouldn't trust a banker with his money. More hilariously, Hadley first doubts Andy's advice on account he was "that smart banker who killed his wife."
It Was His Sled: Andy escapes from Shawshank prison using a plan he'd been preparing for nearly his entire sentence. He escapes by digging a hole behind a series of large posters he had with a rock hammer, smashing open a sewage pipe, climbing through "the length of five football fields" of shit, and spilling out into a muddy river in the middle of a storm, leading to his iconic Redemption in the Rain moment. The details of Andy's escape have been parodied and homaged several times, and the Redemption in the Rain moment is used in promotional materials, which even without context is not hard to guess the nature of.
Magnificent Bastard: Another rare heroic example is Andy Dufresne. Upon discovering the deteriorating condition of the wall of his cell, he slowly (as in over the course of twenty years) carves an escape tunnel through it. Meanwhile, he works his way into the trust of the Warden, who is under the mistaken assumption that he is the Magnificent Bastard. Twenty years later, Andy escapes from the prison, taking a new identity—that he happened to create for the purposes of laundering the Warden's embezzled money, thus making himself a millionaire—and having the Warden and sadistic guard both arrested...all without mentioning a single word of his plan to anyone...not even his best friend. Andy is like the heroic version of Keyzer Soze, and gives us one of the most satisfying endings in film history.
Memetic Mutation: The scene where Andy plays opera music for the prison has been edited many times on YouTube. Said opera music has been replaced by various kinds of music, from pop music to heavy metal, and even by flea market ads. To be fair, the reactions of the prisoners and the warden made it pretty ripe for parody.
The Warden ordering the death of a recently transferred con (Tommy) who has evidence of Andy's innocence, so that Andy will be forced to continue assisting him in his money laundering scheme.
Also, Hadley crossed this when he threatened to throw Andy off the roof and pretend Andy fell off.Beating up the emotionally-overwhelmed inmate earlier on could be excused by claiming he did it to deter other prisoners from making noise, but his later threat has no excuse.
Bogs Diamond and The Sisters raping and brutalizing Andy over the period of several years.
Rewatch Bonus: The surprise inspection scene. The tension. We weren't aware of Andy's digging-a-tunnel project by then. When the warden talks about the poster and almost forgot to return Andy's bible...
The warden keeps his safe and all the damning evidence therein under a needlepoint that reads "His judgment cometh and that Right Soon..." (though apparently the warden's wife likes the less-preferable spelling "judgement")
Andy keeps the rock hammer that facilitates his escape hidden in the Bible, in the book of Exodus.