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.
Frank Horrigan, a Secret Service agent and The Dragon to President Dick Richardson. A psychopath even before his mutation, Horrigan delighted in killing whenever he could. His first onscreen appearance has him gunning down a family, including their child, for refusing his demands. Later, he gleefully kills Brotherhood of Steel agent, Matt, and wipes out the entire community of peaceful, talking deathclaws that the player had earlier befriended. Horrigan has a special hatred for“mutants”, humans and creatures that have been exposed to the FEV virus or even the slightest amount of radiation. This racism leads to him aiding in the Enclave’s plan to unleash a biological weapon which will wipe out all mutated life in North America, in order to make America "genetically pure."
Myron, a chemist who, in exchange for money and whores, invented the drug “Jet” for the Mordino crime family. He brags about having perfected the drug’s recipe by experimenting on about a hundred slaves with heart conditions, killing nearly all of them by inducing heart attacks, and has no remorse for their deaths. Not only does he take pride in how many lives have been ruined by his drug, but, if the Player Character is female and has low intelligence, he will also attempt to rape her by giving her a drugged drink.
Demonic Spiders: Deathclaws are more numerous than ever, and the game introduces the Enclave Soldiers, who will absolutely insta-kill you with their plasma rifles if you're at anything other than near-endgame levels.
Fridge Brilliance: The world of Fallout 2 is unlike most sandbox games in that it actually has an infrastructure that doesn't conveniently revolve around you. In fact, many of the game's quests relate directly to this infrastructure and lets you turn it towards drugs, slavery and general debauchery, lead it into a fragmented prosperity, unite it all under the banner of the NCR or even destroy large chunks of it.
To elaborate on this infrastructure, most of the land's food comes from the large Brahmin herds and farms of Modoc (whose prosperity you can restore, leading to more food, or you can let stagnate, meaning many areas are hard hit) and NCR's own stocks. Vault City and NCR are responsible for training and supplying the majority of the doctors. New Reno is the drugs, booze gambling capital, The Den is home to the biggest slave organisation, Gecko can provide power, and NCR and Vault City have self sustained power. Vault City can give medicine and tech, Broken Hills' uranium mines provide the slugs for the power stations and Redding mines gold which backs the land's economy. You can manipulate the faction's leaders, each of whom has their own ideas of how to further their settlement, and through this the geo-political situation as a whole. Plus, you can encounter and even work for the caravans that carry the land's goods about.
Game Breaker: The Gifted Trait makes character creation a no-brainer. Once a player creates the antidote for Jet addiction, then Jet also makes the player absurdly powerful with no drawbacks. The Slayer and Sniper perks also turn into this by making the player character roll criticals for every attack.
Boxing in New Reno. If you win, you get a perk giving you 12 normal damage threshold, and 4% to all resistances except fire. It is cumulative with armor. Normal damage is anything that isn't plasma, laser, fire, electricity and explosive. Which means that you will take no damage from most enemies, and half damage from most more powerful enemies, without taking armor into account. Most enemies who use laser, plasma, fire and explosives are either using low-tier weapons, using Awesome, but Impractical weapons, or plain non-military personnel (who don't wear effective armor and don't have much Hit Points).
Living anatomy and bonus ranged damage. The former gives you +5 damage against biological targets, the later +2/+4 damage against everything when using firearms or energy weapons. These ignore any form of damage resistance (tested with an EMP Grenade against humans (every non-robotic enemy gains a 500% resistance to EMP). The damage increase is done to each bullet. The best gattling gun (which use extremely rare ammo) fires 25 bullets by burst. Assuming half of them (rounded down) hit (and from close range, they will), you inflict 12*(5+4) = 108 points of damage, enough to kill most target, not counting the normal bullet damage that goes through the armor.
The infamous"Navarro Run". From the second town in the game, it was possible (though very difficult) to trek all the way to San Francisco and get a quest to infiltrate the Enclave Base to steal some Vertibird plans. If you manage to survive all the random encounters (via Save Scumming and a high Agility stat) and get to the base, then you can easily complete the mission without any combat. In addition to getting the Vertibird plans, you're also awarded with a locker full of high end weapons (including a plasma rifle) and a suit of Enclave Power Armor, by far the strongest armor in the entire game, which makes you invincible to pretty much every enemy until you get to the endgame. Since this could be done literally in the first hour of the game, this is completely ridiculous.
It's actually quite difficult to break the game when playing on the max difficulty settings (One setting for combat-only, the other affects skill checks and skill levels), as most end-game enemies will stop missing, aim for the head, and roll criticals more often with their high-tech weapons. Keeping squishy followers alive becomes a real chore, at the very least.
The mighty Bozar. Despite looking like a sniper rifle it is a minigun-type weapon that can be acquired very early, has a tremendous stopping power and uses the common .223 ammo. Acquiring it might take some save scumming depending on your stealing skill and it eats up ammo like there is no tomorrow, but a single blast from it can obliterate most enemies in one or two blasts.
Goddamned Bats: Wolves. You're wandering around the countryside trying to get to New Reno, when you get stopped by three random encounters in a row with wolves. They can't do any damage at all to a decently leveled player, but there's a ton of them, you can't skip their moves, and your companions will likely burn through the ammo of whatever very powerful weapon you've given them to kill things they can just kick! They also have a nasty habit of circling around you and mauling you to death at lower levels. There's also the rats, who stop you from traveling around and force you to enter combat mode until you just step on them.
The random peasant children in the Den are some of the worst Goddamned Bats. They don't do anything but run around and try to pickpocket you, and even unless your steal skill is obscenely high, you'll have to buy your items back from one of the Den's vendors. Yes, this includes quest items. If you want to avoid getting the Childkiller reputation title, you can go with a more moderate option and hit them once. They won't ever bother you again. You can also enter combat mode whenever you are within melee range of the children. They can't steal during combat, so it's not necessary to even hit them.
Probably not exactly a bug, but is still hilarious nonetheless: Wearing a suit of Enclave Power Armor actually makes you better at sex due to the strength enhancement. The fact that you're wearing a full suit of armor with no skin even visible doesn't seem to be a problem.
The broken computer quest in NCR. After Jack has blown himself up, you could repeatedly fix the computer, gaining 3000xp every time. Sadly, fixed in patches.
Moral Event Horizon: Being evil is still kinda OK (although at -500 karma, you get badassBounty Hunters after you). Being a slaver won't make you many friends, but it's a living. Killing children, though, is an irredeemable act that will get you not only bounty hunters but also stop many people from even talking to you.
One-Scene Wonder: Despite having next to no bearing on the actual plot, Sergeant Arch Dornan is one of the most memorable characters in the game. The developers seem to have been intentionally aiming for this, since he has a "talking head" and full voice acting, which is otherwise only reserved for very important characters.
Player Punch: The Talking Deathclaws being brutally picked off by Horrigan For the Evulz, and your entire tribe being kidnapped by the Enclave in order to test their modified FEV. The former can be prevented with the Restoration Project, but doing so requires a seriousSpeed Run.
The Scrappy: First Citizen Lynette of Vault City. The developers were so aware of what an unlikeable, bigoted fascist she was that they added a hidden reward for those who have the stomach to always say exactly what she wants to hear, knowing hardly anyone would ever see it.
Myron is completely devoid of redeeming characteristics, except that to the player he is funny. His level-up quotes are priceless. Lugging him around for the entire game and giving him top-tier weaponry will also make him halfway decent at combat, especially if your character is strong enough that he won't have to fire off more than a couple of shots per battle. Also, he makes Super Stimpacks which are great for killing people without any downsides.
Myron takes this trope to eleven. If he survives the game, the ending says that he got killed by a Jet addict. Even authors of the game hated him.
The Pariah Dog, a random encounter that joins the party randomly and becomes a Doom Magnet for your party.
That One Boss: Frank. Horrigan. Yes, he's the Final Boss, but he's just so damn difficult he fits this trope like a glove. He's a 12 foot tall power armor wearing cyborg, meaning he can absorb tons of damage. He has power armor that deflects just about everything you throw at him, and he's got 999 health (just a little fact: the Final Boss of the last game had 500 health). Not only that, he carries around a Gatling Plasma Rifle that can easily kill you in one hit and moves around faster than a deathclaw, meaning he can attack you several times in one turn. Defeating him on higher difficulties is pretty much impossible unless you either take the Vindicator Minigun with you or talk a squad of Enclave soldiers into joining you and turn his own turrets against him. If you do that, he becomes much easier.
Tier-Induced Scrappy: Myron is by far the weakest character in the entire game. He has extremely limited weapon selection, low health, and will almost always run away from enemies. His only redeeming trait is the ability to make Stimpaks and Super Stimpaks if you bring him the right materials.
Woolseyism: A minor one found in the Russian pirated version of all places (which was also how most of the Russian Fallout fans got into the series, thanks to the official version not being released until 2006), where in start-up loading screens the words "loading" were replaced with something else like (note: translation accuracy not guaranteed): "Get in the line, Sons of the bitches" (where the Chosen One is captured); "Scavengers are immortal" (Guy wearing damaged Power Armor Helmet); "Leave the hope here traveler, you won't need it" (Chosen One silhouetted against car lights); "War, War never changes" and so on. There is also an image where the "Loading" was not replaced, since it kinda fitted the image. The alternate title "Vozrozhdenie" (Rebirth, Revival) may also be this for some, if only for intended irony.