I'm am firmly in the camp that this card is a must-add to literally every deck, (ok, not Carolyn.) Tutors like this are just so efficient and smooth out clunkiness. It isn't a splashy or fun card, but you'd rather run this than a less apt weapon for your deck. Run 3 to 4 weapons and a playset of this card. Yes, you can run it with 3 weapons just fine, you'll hit a weapon a vast majority of the time and you're not building your deck fretting over 5% ~ 10% chances. It makes upgrading into better expensive weapons like Flamethrower better at every stage of the game. It helps you fetch any character-specific weapons. If you're playing at higher difficulties, it really is necessary.
Tactique.
Cherchez un soutien Arme parmi les 9 cartes du dessus de votre deck et ajoutez-le à votre main. Mélangez votre deck.

I wanted to like this card. For a long time I used to run 2 copies of it in Guardian builds. Then, after a while, I started running only one copy of it (which is not something I normally do with cards) - and now I generally omit it altogether.
The reasons why I used to include this 2 copies of card at first:
- In other card games, "tutor" effects (cards that search your deck for other cards) are normally powerful because they let you search your deck for things that you really need, adding consistency.
- After you draw a 5-card opening hand of a 33-card deck (standard for most investigators after adding signature cards and weaknesses), you are left with 28 cards. Prepared for the Worst lets you search the top 9 cards of your deck, so that's just under a third of the deck, which is not bad.
- Weapons are important. If you're without a weapon and your role in your group is to kill things, you can get overwhelmed really, really fast.
Why I ultimately stopped including this card altogether:
- The cost for using this ability is one card, one resource, and one action. That's really expensive for what it does, especially considering you then have to spend another action and more resources to play the card that you found using its effect.
- It's not even guaranteed to succeed! When it misses, it really hurts. It's also least effective at the beginning of the game (as you have the most cards in your deck) and that's arguably when you need it most, since the beginning of the game is when you're setting things up.
- Efficiency-wise, it's often better to just have slightly cheaper weapon that you can use until one of your primary weapons come up.
- In my experience, if you have 4 good weapons in a 33 card deck, you have a reasonable chance of getting one in your opening hand if you mulligan specifically to look for one.
Why I used one copy of this card for a little bit:
- It has good synergy with Stick to the Plan since it has the Tactic keyword and it's a card that can help you early on in a scenario. It increases a deck's ability to start reliably well.
- Two copies just seemed excessive since the second one will normally be not very useful.
This card preys on weapon anxiety - the fear that you'll end up with no weapons when you really need them. I don't think this card is the answer to weapon anxiety, though - it's too expensive, too slow, and too unreliable to guarantee that you'll get the weapon you need. The only use I can think of for this card would be if you really want to use it to try and fish out a big gun - think Lightning Gun or Flamethrower - at a midway point through a campaign when you've already bought one copy of the big gun and don't have enough experience yet for a second copy. Even then, though, my advice would still be to simply use other weapons to keep yourself going until your big gun shows up.
Unless some other cards come out to make this more viable or desirable, I would say this card is probably worth passing on for the time being.
Edit: Updated for the times.
TL:DR. Slotting Prepared for the Worst is worse then slotting another weapon if your goal is to have "any good weapon". Slot Prepared for the Worst only when you want to consistently field a particular weapon (Lightning Gun for example).
Prepared for the Worst, pretty good card, but only required in some pretty specific builds.
So, "tutor a weapon", really great for those times where you want a weapon in your hand, yeah? In deckbuilding Prepared for the Worst is largely interchangeable with weapons, card for card.
Here's the thing, if you want a gun in your hand. And fill your deck with guns, why bother with this thing? On one hand you play with so and so many guns and have this thing in your deck, spend an action and a resource (and card!) to fish for the gun, and THEN play the gun. Why not just, skip this damn thing, put 2 more guns in your deck, draw the gun straight from the start rather then bothering with this middle man?
So. For the explicit purpose of having a weapon, Prepared for the Worst is a hoop you just dont need to jump through anymore. There's a literal plethora of viable weapons now! .45 Automatic and .45 Thompson and Machete and Enchanted Blade and all the out of class stuff too! You can easily have a deck that's 50% weapons!
That said, Prepared for the Worst is still a great card, it just has a more defined purpose these days. The real point of Prepared for the Worst is not to ensure you have a weapon in your hand. The purpose of Prepared for the Worst is to have THAT weapon in your hand, you know. KNIFE!!! I kid, I'm of course talking about that investigator strength gun like Jenny's Twin .45s or Detective's Colt 1911s or a really big XP device like Lightning Gun or Flamethrower.
Bonus: It doesn't hurt that when Prepared for the Worst isn't needed for it's explicit purpose, you can chuck it at an investigate or fight action.
I figured most people know the optimal policy for this card by now, but getting it into a review of the card itself will help out newer people.
TL;DR:If you are using this to run only two weapons and benefit consistently from high XP weapons, you should mulligain discarding anything that is not a weapon if you didn't open with one, and then on your first turn spend all your actions drawing, and then your second turn spending two drawing and then playing this card.
Most modern guardians run 2 weapons (maybe 3 if a signature is a weapon) and two of this early, and then sometimes going down to one of this on Stick to the plan because, if you use it correctly, you will have a 90% chance of getting one of your two weapons in the first two turns using this card.
If you 'hard mulligan' (discarding literally any card that isn't your weapon if you didn't open with a weapon) you have a 55% chance to find one of the two copies of your weapon in your deck. If you don't find it in that pool, and then go for it with prepared for the worst, you have a 55% chance to find one of the copies in the top 9 cards. This means that you have an 80% chance to find the weapon, but that means 1-2 games a scenario you will fail to have your weapons in the first two turns of the game, which can get... rough, especially because if this card misses you didn't thin your deck and now will have a hellish time finding your guns.
But if you instead take your first turn entirely drawing cards, and then on your second turn draw 2 cards and play this, your odds increase, and Prepared for the worst plus the draws will find your weapon 79% of the time. Combined with the hard mulligain and you will be starting with your weapon, which means you find those guns 91% of the time. If you really slow-roll and play this turn 3 (perhaps playing an ally on your 6th action, but still getting your upkeep draw) you will nab it 95% of the time, meaning you will proably never fail to get your gun by turn 3 in any campaign, though this may lean on your flex-evader in a 4 man group.
Compare to just trying to draw into your weapon manually using the same policy. On your mulligan you got the same odds, but if you spend an entire two turns drawing you will only find a copy of your guns around 40% of the time, meaning in total you have about a 20% chance to brick out on the first two turns. So you are probably going to fail to find your weapon once, maybe twice in your campaign before turn 3.
What is worse is that the realities where you brick your mulligan can be far worse. You will fail your mulligain about 50% of the time. If you do, you still find it by the end of turn 2 50% of the time, but you have a 20% chance to take 5 turns to find your gun, meaning that a little under once a campaign you will be unarmed for half a scenario, if you can even afford to spend 4 turns doing nothing but drawing! Once you need to start doing a bad Nathaniel Cho impression your rate of finding your weapon becomes much worse and it becomes realistic you will never see a copy in a game if you need to give up by the end of turn 2.
And if you fire this off turn 1, you have a 60% chance of bricking there, and if that happens you enter the 'draw and pray' statistical reality and suddenly you start risking trauma once or twice in your campaign because your gun never shows up. So really, take it slow and don't Hail Mary Prepared For the Worst turn 1 hoping your weapons are in the top third of your deck, get it to the point where they only need to be in the top half and this card will make you a much happier camper.
This card is a huge difference maker in 2 weapon decks if used right, it is probably Guardian's most meta-defining card to the point it makes it really hard for the designers to make any sort of 'mid-grade' or 'backup' weapon in Guardian and heavily warps the card pool, but if you use it wrong it is going to make you miserable compared to running 4 weapons.
Commenting because I don't see this point in the other reviews - I believe this there is great synergy between this card and Stick to the Plan SPECIFICALLY when you are also running 3 of Astounding Revelation. You get your first Astounding Revelation when you set up Stick to the Plan before the game even starts. You can have 1 copy of Prepared for the Worst in your deck and attach it to Stick to The Plan. Whenever you need to search for a weapon you have a decent chance of getting your second Astounding Revelation. By playing only one copy Prepared for the Worst and Sticking it to that Plan, you also avoid the dead draw of a PFTW when you don't need more weapons.
If it's your first play of the game you have a 60% chance of finding one of the two Astounding Revelations in your deck of 25 cards.
If it's your first play of the game and you have no weapon in your opening hand, you have the following probability of finding at least one weapon in the 9 card search:
6 in deck: 95.24%
5 in deck: 91.8%
4 in deck: 85.6%
3 in deck: 75.7%
2 in deck: 60%