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.
Deconstruction: Of You Killed My Father and Roaring Rampage of Revenge. One would think that it's a Bittersweet Ending since Jack got his revenge but it's undone when you realize that John's wife, one of the people John started this entire endeavor for, died a few years later, possibly due to the depression of losing him. Meanwhile Jack, in his search for vengeance, has adopted the lifestyle John was trying to protect him from. Many of Jack's gameplay quotes indicate his life is pretty hollow. On top of that, no one other than Jack will ever know the truth about John Marston's redemption and Ross's betrayals. Not only that, but, in the end, the act of vengeance shows that Jack became exactly the man John didn't want him to be, that is, a man like himself - and one of his quotes shows that he gave up on his dream of becoming a writer and lost his idealistic spirit.
Cougars. One-Hit Kill in multiplayer. Virtually silent in the snow. Not fun.
The cougars in particular get an excellent Establishing Character Moment highlighting their deadly stealth in one of the late-game story missions (see Shmuck Bait below).
Both cougars and bears each have a certain tiny area on the map where multiple copies of the animal spawn until a "legendary" version of it pops up. This means you may be forced into running laps around a cabin with a dozen hungry pumas behind you.
Packs of wolves aren't exactly easy, especially since three or four of them attack at once.
For a human example, those guys with shotguns who always seem to be at such an angle that you can't shoot them from outside the room they're in.
Or the guys who have RIDICULOUS accuracy with the Springfield Rifle. Both of these guys are usually named Gus Ballard or Slink Bradshaw for some reason.
Landon Ricketts is very popular as well, especially considering hes only featured in four missions. Rockstar received a large amount of complaints for not including him as an online playable character.
Averted with French (well, what little we see of him.) His nationality is only known by his nickname and him being said to be French by others; he lacks an accent. John even comments on this when talking to Irish later on.
Game Breaker: In one of the side missions, you are asked to play Liar's Dice against a man in Thieves' Landing, in order to get the deed to a property. The collateral on the deed is $200, so technically he puts down $200 every time he plays (even after you get the deed). Also, this guy is TERRIBLE and never runs out of money, so a half-hour to an hour and a three year-old's skill at Liar's Dice is all that's required for all the money you could ever want.
Wolves. They always attack in groups, they're just enough of a threat to be dangerous to ignore, they follow you relentlessly and they have a major talent for showing up while you're hunting for something else.
Cougars are far worse, especially around Beecher's Hope, where they're ridiculously common, and where you'll be spending most of the final one or two hours around.
Wolves also have the ability to latch onto your gun arm with their teeth, usually right before you take you can shoot them. And every time you've finally killed all nearby wolves and stop to skin them, you'll find out 2 more were just behind that rock.
And on the flip side, a talking dog (complete with a Mexican Accent) that hands you a shotgun upon meeting it, and that's also strong enough to give you an ally-oop up the wall and into the enemy gang's hideout. Oh, and it levitates too.
After the mission in Mexico where you must board and stop a moving train before it goes across a boobytrapped railroad bridge one can still hop on a train and ride, without stopping, across the gap where the destroyed bridge was. It's surreal, to say the least.
Ah, the Handheld Self-Propelled Homing Dynamite Grenade! The weapon of the discerning cowboy!
With the release of the DLC, free roam games would not spawn any NPCs anywhere, which meant that merely approaching a gang hideout would cause it to instantly complete. Replay ad nauseum for infinite XP.
A nice time saving bug is that you can skip the skinning animation by having your horse stand on top of the animal carcass.
Hell Is That Noise: Can happen when you hear certain wild animals for the first time but can't see them, and they don't sound too happy to meet you. Recognizing what animals made the sounds lead to Oh Crap moments. Also, sometimes a woman will scream bloody murder, and you know something is terribly wrong.
Jack Marston is considered this in some internet communities. For one thing because he's an annoying kid, and for another because his missions revolve around the mountain. Oh, and because he takes over as the main character when you finish the story, with no way to play as John Marston again outside of loading an old save or starting a new game.
And while many consider Herbert Moon the Ensemble Darkhorse, many hate him to an extent that they consider him this. He is truly the love him or hate him character of Red Dead Redemption. He makes a return in Undead Nightmare to show us more of what we love about him, his homophobia, antisemetic, xenophobic, sexist and racist attitudes. Then you get to see zombies eat him.
Harold MacDougal, easily the most annoying character in the game, mostly because of the sneaking suspicion that we're actually meant to find him funny. This idea that his racism is a quaint old ineffectual footnote in history that we can all laugh at doesn't quite gel with the broader subtext of the story at that point and your role in it (i.e. helping the army force it's way into a Native American settlement and slaughter everyone inside). There's also they way he treated Nastas.
They seem to have realised this and in Undead Nightmare, he's killed by an Undead Nastas.
While not as scrappy, pulling out your weapon will freak the entire town out, even if it was accidental.
Surprisingly Improved Sequel: Red Dead Revolver had a great soundtrack and atmosphere, but the gameplay, while fun, didn't really stand out from the crowd. Red Dead Redemption, however, features a beautiful and wide-open world to explore, much more to do, and an arguably better storyline, while losing none of its predecessor's strengths.
Poor Nastas is treated badly by everyone but John.
The entire Marston family. And the only surviving member, Jack, is a depressed loner whose dialouge expresses that he doesn't have much to live for and rarely says anything optimistic. All his dreams of making something of himself and becoming a writer are gone. His act of revenge towards Edgar Ross puts him on the path towards being an outlaw that his father died trying to ensure wouldn't happen. Downer Ending, no matter which way you look at it.