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.

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.