The ability to pick up and move world objects in 3 and New Vegas isn't necessary, but is useful for finding hidden items, climbing to otherwise inaccessible areas, lugging excess Vendor Trash around or carrying stuff out of sight to steal. The only time either game ever explains how to do it is in a minor, easy-to-miss unmarked quest (A Final Plan for Esteban) in New Vegas.
The Pip-Boy flashlight in the later games is never mentioned in a tutorial and only briefly brought up in loading screens, so it's quite possible to not even know it exists until you need it (and maybe not even then).
To get some of the unique apparel, armor and weapons in 3, New Vegas and 4without killing NPCs, you will have to reverse-pickpocket them, which is the act of placing a like-minded item in their inventory. This is actually a trend that started in the first game, but was expanded in later entries — however, the only way you'd ever be clued into this is in 3, with an achievement ("Psychotic Prankster") that is awarded for planting a live grenade or mine in the inventory of an NPC. Even worse, if you want a unique piece of clothing or weapon held by NPCs in the latter entries, it's not as simple as stuffing a random gun or piece of armor in their inventory. The item in question has to have a higher Damage Threshold or weapon damage than the item you are trying to obtain. Nothing in the games indicates this.
In the "Tranquility Lane" quest, you and your father are trapped in a simulation with a sadistic Mad Scientist and several innocent people. Completing the quest is pretty straightforward, but if you want to do the right thing and "save" the people, it gets tricky. You're told that there's a hidden terminal, and you're given extremely vague hints and a bunch of seemingly random objects to interact with. Have fun with that.
The Arefu quest Blood Ties has only one counterintuitive way to successfully complete it. You are sent to find a gang known only as The Family because they have been terrorizing the settlement of Arefu. And they have kidnapped an Arefu resident Ian West. When you find them, you find out that The Family were formerly cannibals but have now reformed into strictly being hematophage vampires. With a good enough Medicine skill, you even figure out that two murder victims in Arefu were victimized by someone who drank their blood. And terminal entries even suggest that they do not outright attack anyone to feed but instead bait victims into attacking them via vandalism so they can feed only in self defense, with the leader even stating that Arefus time will come, but if you kill any Family member after busting out their captive Ian, you get a message stating that Arefu is hostile to you and the mission fails. To complete it, you must work out a deal wherein Arefu is protected by the Family in exchange for Blood Packs. This is because once you speak to Ian in his cell, the game prematurely links Arefu and the Family as one faction, making an attack on one as an attack on all. If you want to kill The Family and complete this quest, you must kill all of them before freeing Ian. This includes their gate guard who is a bit of a walk away in the opposite direction from Ians cell and thereby easy to miss. Massacre the Family in its entirety before speaking to Ian and the quest completes.
There's a lot of skill books lying in various places, sometimes hidden in places you're unlikely to visit if you're not trying to scout every inch of the map, but the Grognak the Barbarian book located in Canterbury Commons takes the cake: not only you must pickpocket a NPC to acquire it (something most good players wouldn't think of), but the book is carried by a child, while children are normally unable to be harmed in the game.
Fallout: New Vegas
Forget about trying to get even a moderately good ending without a strategy guide memorized and open at every quest. Not only can you not start certain quests, but if you complete some quests then it means you either can't complete others or will have no way of getting a Good Karma resolution. Bear in mind that the quests you'll already have completed may have been at about the 1015-hour mark, and the quest you now can't complete/start/get a good ending for comes around the 40-hour mark, and nowhere in-game is there any indication of which quests invalidate others (e.g., "Aba Daba Honeymoon" can be rendered unfinishable by the dialog at the end of "I Put a Spell on You").
The quest "I Fought the Law," which most good-inclined players will miss because they're likely to side against the Powder Gangers from the start, and because the inhabitants of the NCRCF will be hostile to them, making them likely to kill Eddie and immediately fail the quest. Or one might kill him because he's got a plasma pistol. Then again, the quest is bugged and leads to a bad ending even when it should be a good one, so that's for the better, really. Additionally, if you want the NCR to retake the prison, you have to work for the Powder Gangers until you're told to investigate the NCR's plans, then you have to switch sides and betray Eddie and help NCR attack the compound. Just waltzing into the compound and gunning down everyone yourself, which you're liable to do because again, you've probably made an enemy of the Powder Gangers, denies you the option to just turn over the empty prison to NCR when you're done.
"I Put a Spell on You" is almost legendary for its unintuitive nature, aside from a plethora of bugs. Long story short, there's a spy somewhere in Camp McCarran, and you've been tasked to single him out. After finding out there have been late-night sightings at the comm tower, you have two mission arrows: one to the comm tower, and another to the man you're working with, Captain Curtis. Since Curtis is the spy, talking to Curtis and telling him your lead makes the mission practically unwinnable, since he will attack you in the tower instead of radioing his contact, thus you won't know if he will bomb the monorail. There is no hint that doing this was wrong, and there is no way other than using the console to set the winning value back to 0. Ergo, by following the directions you have failed the quest. You could still side with the Legion, in which case you do the same quest, but instead are helping Curtis out in his plot to bomb the monorail. This is arguably the better path, as not only is it relatively easy, if done right it gets you an exploit for infinite caps. But if you start along that path, you're committed to bombing the monorail as soon as you collect the bomb. Want to play the Legion version of the quest? You can't be too hated by the NCR, because Curtis is coded as a Ranger, and will see through your NCR disguise and attack you just like any other NCR Ranger, even though he's a Legion spy. This makes it impossible to talk to him.
Some of the Companion Quests are nigh-impossible to complete (or even know about in the first place) unless you have an online guide handy. Several of them require you to speak with specific people at very specific points at the game, and this is never mentioned to the player in any dialogue tree.
Raul's is one of the worst. To complete his quest, you have to talk to three specific people in the wasteland. There are no quest markers or any indication of who you should talk to besides "some old guys". Plus, before it was patched, talking to any of them before you have Raul in your party or when Raul is not in your party meant the quest couldn't be completed. Even worse, it's buggy as hell, meaning that even if you know who to talk to, some bug could cause the dialog with Raul to not be initiated, or for the NPC to disappear from the game entirely in the case of one of the NPCs.
For Boone's quest, you need to accumulate 5 "history" points by completing various Legion-related events just to trigger it. None of the events are repeatable, neither the events nor points are mentioned in-game, and Boone must be in your party when you complete them. Completing the events without him renders the points, and potentially the quest, Permanently Missed. And some of the events have to be completed in conjunction with separate quests to earn the points. The sidequest "Booted" deserves a honorable mention here, because doing things in the seemingly correct logical order without even trying to break the game will waste 2 of those points without even having unlocked Boone as a follower yetnote The quest starts in Nipton, after finding Boxcar the Powder Ganger, and leads you to a Legion camp located between Nipton and Novac. After reaching Nipton, the main quest tells you to head to Novac, and "Booted"'s objective is located next to the most direct road to your destination. Every new player will do the quest at this point, and there's no way to guess it's related to Boone, a NPC the game doesn't mention at all until you reach Novac. And even if you've earned the necessary points, you also have to speak about a certain topic with a specific NPC to access the dialogue option with Boone that triggers the quest.
Veronica's quest is similar to the first two, except buggy as hell. There are nine places in the wastes where you can bring her in order to trigger dialogue. Of these nine, only four are permanent (the remaining five are lines of dialogue from the first time you meet the NPC). Assuming you even know where to look, Veronica may take days to finally remember she's supposed to say something, so you can't trigger the quest until she finally decides to do it. It seems to work better if you meet her request for a dress first, but that in itself is an example of this because the type of dress she wants is the kind worn by the White Glove Society, and you have to kill or reverse-pickpocket a member to get one if you don't follow a specific line in the quest. Not to mention that obtaining either one of the two weapons in the quest will force start the quest, but in a way that they can't be completed even when completed, since you still have unfinished business earlier in the quest.
Arcade Gannon's quest, like Boone and Veronica's, also requires a number of fairly random triggers in order to initiate, and can be broken via bugs by accident.
Dean Domino's recruitment conversation is the worst of the lot, as it is very likely that you'll cause Dean to betray you later on in the DLC during your first chat with him. Getting Dean to not turn on you is downright contrary to the very logic of the game, though it does make sense from a character perspective; Dean has a very fragile ego, and not treating him with absolute respect or being better than him at anything is obviously grudge material and will cause him to betray you later. But why this conversation in particular? In the very first conversation with him, you come to a choice between a Barter skill check and a normal dialogue choice. Almost any player will obviously pick the Barter choice if at all possible because skill-requiring answers are usually (and should be) superior to the ones available to all characters. However, in this case, picking this choice will make it impossible to get him to side with you inside the Sierra Madre, no matter how well you talk to him throughout the adventure. Made even more egregious by the fact that the Barter dialogue choice is simply informing Dean that he isn't bargaining from a position of power because your collars (and thus lives) are linked and he basically doesn't have a choice but to work with you... which is precisely the truth!
The challenge "The Whole Sad Story" requires you to learn how each of the four other characters in the DLC got to the Sierra Madre. For Elijah, Christine, and Dean, you just have to be sure to exhaust all dialogue with them. Getting Dog/God's part however, the conversation path is only available to your character if you have less than 4 Intelligence. Good luck figuring that out without looking it up.
While it is possible to obtain a single bottle of Nuka-Cola Quantum (found much more liberally in 3), doing so requires you to know that it only appears in one location - a trunk in Hopeville, with a 10% spawn chance. If you don't get it on that first try, you're out of luck. Short of Save Scumming (and having to listen to a speech repeatedly before you get it), you may never realize the item was intended to be in the game in the first place.
The best ending for the DLC is achieved by allowing the Divide version of ED-E to perform a Heroic Sacrifice to stop the nuclear missiles from activating and destroying key NCR and Legion strongholds. However, doing this ending automatically locks you out of two locations (the Long 15 and Dry Wells) which offer high-level bosses and loot. Nothing in the game clues you into this beforehand besides their markers showing up on the world map if you have the DLC installed and have chosen the Explorer perk. The only way to access both of these areas is to nuke both targets, which causes a significant reputation loss on both sides and can put you on one or more faction's hitlists instantly. note If you do this quest BEFORE confronting Benny at the Tops Casino, Vulpes Inculta/Alerio gives you the Mark of Caesar right afterwards, thus removing any negative reputation you may had with them. Later, an NCR trooper does the same when given Ambassador Crocker's note.
The settlement system only has one extremely bare-bones tutorial, which introduces you to the three basic things a settlement needs (food, water, defense), as well as the basics of assigning settlers to a task. It does not touch upon surplus resources, the nuances of the happiness system, or even basic house construction. The only other hints you get are from tips on the loading screen and the description of the Local Leader perk, the latter being vital to larger settlements and to propping up new settlements. The game only tells you once that the defense rating has to be kept equal to or higher than the total amount of resources being produced by the town, and it never tells you how to set up a power grid how? build generators then connect them to objects by attaching wires. Pylons and power conduits (the latter of which provide energy to lights without the need for wires as they are wall mounted) extend the reach of wires, how shipments of junk work how? shipments, such as aluminum, act as 25 or 50 units of said item in the workshop. For example, you need 12 aluminum units for your power armor. You have a shipment of 50 in your inventory. By putting the shipment into the workshop, you now add 50 units of aluminum. 12 units is spent. The new total of aluminum units is (50+x)-12=y, with x being "total before the shipment" and y being "total after the spent units", or how food/water surpluses and junk are shared (or even that they can be shared).how? To do so you need to assign settlers to supply lines (only after you have rank 1 of "Local Leader"). To do this you highlight a settler and press press [Q] (or RB/R1 on Xbox One/PS4) to chose where they go. Junk, miscellaneous stuff, food, and water are then shared to the settlements connected. Settlers assigned as Provisioners also act as armed patrols between supply lines if given good enough arms and armor.
With Local Leader rank 2 "You can build stores and workstations at workshop settlements." Sounds good right? Now you can assign settlers to work stores so you can have an easy access to caps and stores to get supplies and drop off crap and Cap Collector can let you build the best stores. But there's one thing they don't tell you: Level Four Traders. These 8 people are scattered across Boston, some being random encounters, and can live in settlements. But these settlers upgrade Level 3 stores to Level 4 stores, boosting the amount of supplies and giving access to rare items. You will be completely likely to just leave them to work on farms or jobs they are poor at because this detail is never explained nor mentioned.
In order to get into the Institute, you have to build a relay platform using the settlement interface. This seems simple on its surface, but several of the specifics can be confusing. The platform itself consists of a large, three-pronged cover and a smaller platform, the latter snapping onto the former, which the game doesn't make clear. The operating console has to be within earshot of the platform so the operator's dialog will register and move the quest along. Finally, all three parts have to be on the same power grid.
Though the story missions do tell you outright when you're going to make a faction hostile permanently, the intertwined nature of the missions mean a lot of them can conflict with each other even before you've reached a turning point. For example, one Brotherhood mission causes the Railroad Assaultron P.A.M. to enter a "security lockdown" mode in which she will not respond to any attempts at conversation, even if you have quests to turn in. Furthermore, this will happen even if you haven't fulfilled the first objective of speaking to the quest giver. The conversation priority system, which determines how characters respond if there's multiple options, will also prioritize secondary objectives of other quests over that character's personal quests. For example, when Institute quests give you the option to warn the Brotherhood, this warning will be prioritized over any quests you may have active with Maxson.
Keeping all of the non-Institute factions and their related companions in play through the ending is possible, but requires a very specific order in doing quests for all three factions with very specific cutoffs that can make the A-Ending requirements from Valkyrie Profile seem sane. And even then, doing the wrong things during the final mission can permanently anger certain factions companions into leaving you. Doing so will also make you miss out on endgame rewards from the Brotherhood and Railroad. This is how it's done.
The game doesn't tell you that Critical Hits always hit, and there is a non-trivial difference between "more powerful attack" and "more powerful attack that never misses."
The game never tells you that the Railroad faction will refuse to work with you anymore if you dont do the mission Boston After Dark parts 1 and 2 immediately after their intro mission Tradecraft. Since they are required to decode the Courser Chip for the main quest, pissing them off this way requires you to Kill 'Em All and decode the chip using an owned terminal to proceed.