If beheading was the surefire way to kill a monster (say, a vampire or a changeling) what kind of weapon would be preferable in a modern setting? I was thinking of something like an axe or a tomahawk, but would they be better than, say, a short sword?
In a modern setting? My first thought would be a 12 Gauge bolo shell. These are a pair of 12-15mm slugs connected by a metal wire. When fired, the slugs will begin orbiting one another, and the resulting projectile will cut through soft objects, like small trees, trash cans, car doors, and human bodies with relative ease.
There’s a simple problem here. If your monsters are superhuman, going into melee with them is a death sentence for an unmodified human. This is especially true if your monsters are significantly faster than normal, though superhuman strength that allows them to simply rip limbs off will quickly disarm your swordsman, no matter how good they are.
“Safely” dealing with monsters requires that you step back, evaluate your options, and pick the best tools for the job. With rare exceptions, that’s not going to be a sword. They may use a fireaxe to finish the job on a downed monster, but putting those things down will be much safer at range.
If your monster hunters have access to military grade hardware (and can use them without drawing heavy police scrutiny), then an excellent option would be FRAG-12 shells. These are a grenade round designed to load into a 12 gauge shotgun, and should be able to spread your unsuspecting vampire all over the walls.
If your monsters have particular weaknesses, then finding a way to deliver those at range will be far safer. For example: silver bullets are a real thing. They don’t make for fantastic rifle rounds, because the weight is lower than lead, impairing the ballistics, but if you need silver to get the job done, a handgun is a legitimate option.
Explosive and incendiary options can be delivered precisely, and at range. This can be anything from a Dragon’s Breath shotgun shell, which ejects flaming metals (specifically, highly reactive metals which ignite on contact with the atmosphere), or flare shells, to home-made explosive handgun rounds. (For example: Adding a fulminated mercury payload to a hollow-point round, which is an incredibly dangerous, but quite real, option.)
Hell, against a monster that’s unusually light sensitive, just chucking a flash bang in could seriously mess them up.
So far as it goes, a simple 12 gauge pump action shotgun, may be able to down a monster, giving your characters time to take its head off. Though, that is an inherently risky strategy, because they don’t know exactly how long it will stay down, and will need to get within arm’s reach.
There’s a slight difference here, between monsters and normal opponents: Humans, when presented with gunfire, will die. Monsters, particularly something that’s undead, may not. The basic idea behind a bullet is you’ll poke holes in something and let it bleed to death. If they thing you’re shooting can’t die from bleeding, there’s a real possibility that shooting them won’t get the job done. Makes sense. Except, that’s not the same thing as being immune to gunfire. A bullet that strikes bone will still break it. Shooting a vampire in the head may not kill it, but hosing one down with automatic rifle fire should still mess it up enough to put it down, at least for a few minutes (if not longer).
Incidentally, if you’re working with the idea of monsters that are, literally, fast enough to dodge bullets, long range rifle fire is your friend. Firing at ranges where the sound will not reach your monster before the bullet means they won’t know to dodge it. For example: A .50 HEAP round should be able to debone your monster from the next zip code over. Again, as above, this is military hardware, and the original intent for HEAP rounds were disabling vehicles and aircraft, but vampires are generally a lot less threatening when they’ve already been disassembled for easy storage.
As I mentioned earlier, for decapitation of a downed opponent in a modern setting, my money’s on a fire axe. It’s nice, large, heavy enough to get the job done, and common enough that your characters could potentially grab one on the scene. If your characters aren’t squeamish, a sledgehammer to the skull may also finish the job (depending on your monster).
So, I’ve been talking about high end hardware, for the most part. If your monster hunters have the backing of some group that can kit them out. If your characters are just people off the street, faced with monsters, and have no protections, things can get a lot dicier. Dealing with cosmic horror, when you can potentially call in an air strike, is a lot less threatening, than when you’re dealing with the idea that your neighbor has come back from the grave, and is preying on your family.
If your setting is one where your monster hunters are just, “normal,” people, then picking your tools becomes more important, but you also have way less options, and anything they do will draw police attention. Luring a monster into an abandoned building, and setting fire to the place may kill it, but that’s also a good way to get arrested. Meanwhile, things like HEAP rounds, FRAG-12s, and FNX-45s loaded with Silver Bullets are way outside your budget.
If that’s the situation your characters are in, things like fire axes, or maybe an old 1911 are options, but if your characters have normal considerations, spending $30 a round, to load that .45 with silver is probably not a realistic option.
For writing this kind of desperate, street level monster hunter, one of my favorite reference sources is still Hunter: The Reckoning. There’s also some good advice on story-building mixed in, and the old World of Darkness remains an excellent urban fantasy setting, with a lot of moving pieces.
For government funded monster hunters (specifically vampires), Ultraviolet (the British TV series, unrelated to the 2006 American film of the same name) is an excellent examination of how modern technology can intersect with the supernatural. (Also, the first place I ran across Idris Elba.)
Regardless your approach, the best options for dealing with monsters in a modern setting are going to be getting creative with modern technologies. This may be as simple as tazering a werewolf, or chucking Molotov cocktails at a vampire.