Generally, equipment doesn't mean a damn. You are not your fucking magnum. Generally.
There are two exceptions:
Adults carry +1 when using the most effective equipment for the job.
Teens carry +1 when using the most fitting equipment for the moment.
But astute readers will be in an uproar, surely! NPCs don't roll dice, so what is that adult +1 good for? Here's how: that +1 is fluid. Let's unpack an example:
Sheriff Dawson has wised up to Jason's situation. So when he pursues Jason into that locker room, he tells his men to hang back. And he pulls out his other pistol. The one with the silver bullets, each one sporting a cross crudely carved into its tip. Sheriff Dawson carries +1.
Right, so Sheriff Dawson doesn't roll dice. But he's pursuing Jason with a silver-bullet-and-holy-crosses pistol. So, "Jason, what do you do?" If Jason tries to seize something by force, and Sheriff Dawson is going to bring that gun to bare in process, then Jason is acting at -1. If Jason gets shot and then tries to get away, he's at a -1 because there's silver coursing through his veins.
Sheriff Dawson's +1 can be applied against a roll Jason is making. It can also be applied toward harm that Dawson is doing. That +1 is fluid, and it applies in the instances where Sheriff Dawson's equipment is most effective for the job.
If this sounds familiar, this fluid currency thing, you've read Sorcerer. It's a game about Infernals, only they call them something different.
Alright, teenager example:
Anita ("Needy") is straddling Jennifer, on her four-poster bed. She's got a boxcutter in her right hand, and is struggling to plunge it into Jennifer's heart. Yes, a boxcutter. Needy isn't the tried-and-true murderer here; she grabbed the only thing she could - something crude, and frail, but dangerous nonetheless. Needy couldn't have picked a more fitting murder weapon - it is a mirror into her state. It's poignant, or near fucking close. She carries +1 for it.
If Needy is a PC, then she just applies that +1 to relevant rolls, and to harm done. If she's an NPC, then it works like it does for Sheriff Dawson at this point: that +1 is fluid.
I stole that example from Jennifer's Body, by the way.
When you do harm to someone, if you're using your bare fists or a glass bottle or you're kicking at their groin, it's 1-harm. If you shove them down a small flight of stairs, or throw a chair at them, or ram their truck off the road but it doesn't flip, it's 1-harm.
1-harm is the kind of stuff that people gossip about in the change room.
If you shoot them with a gun, or you have giant fucking claws, or you get a solid hit to the temple with an aluminum bat, it's 2-harm. If you set fire to their house and they barely escape, maybe having to body-check a smoldering door in the process, it's 2-harm.
2-harm is enough to require medical treatment. It'll get you a couple days off school, if you let people know about it. It'll have the cops at your door, if it's reported.
If it's worse than that, and it's gotta be pretty bad, it's 3-harm.
3-harm is enough to make front page news, and to scare the shit out of the community, and to make small-town nurses queasy. When someone leaves someone else for dead in a movie, that's 3-harm.
Now, remember that adults can add +1 harm if they're using the most effective equipment for the job, and teens can add +1 harm if they're using the most fitting equipment for the moment. This +1 isn't factored into those break-downs above.
Harm & Theme
Monsterhearts isn't a game about vampire hunters sporting holy-water grenades, or special ops teams with assault rifles. It's about fucked-up teenage monsters.
It's important to keep your gun fetish out of your Monsterhearts game. If you're slinging 3-harm around, you better have a good thematic justification for doing so.