I don’t think any weapons would “reemerge.” I mean, we talked about how a bow is out of the question a long time ago. Actually, I’m going to step back a bit. “Dystopia” has become a keyphrase for fascist/authoritarian lately. Any sufficiently bleak setting can end up as a dystopia. Strictly speaking, there’s an entire subgenre of postapocalyptic stuff that falls into that range, along with a fairly large chunk of the cyberpunk genre.
The reason I’m bringing this up is because guns tend to remain in circulation in those settings, even if they’re illegal to own. It’s fine to say that the governments of the world outlawed firearms, but that doesn’t explain how they managed to round up the roughly half a billion firearms in circulation.
Even if you say the police respond more harshly to gun crimes, for example, summary execution for suspicion of possessing a firearm, then that removes the veil of authority and turns the police into just another inner city gang, to be killed on sight, albeit a better equipped one. This is actually a problem police face currently, in some major cities, like New York and Los Angeles.
Anyway, stepping back from that, any other weapons? Honestly, this is going to read more like a list of improvised weapons. Because almost anything can be used to kill someone else, this is by no means exhaustive.
Anyone with a belt sander and a piece of scrap metal can make a shiv, knives aren’t going anywhere, and they’re easy to conceal.
Even if we’re talking about a post-apocalyptic setting, improvised flamethrowers and cattle prods should be fairly easy to rig up, for anyone with some decent metal working equipment. Getting good fuel for a flamethrower could be an issue. It can’t be something too corrosive that’ll eat through the weapon’s feed system. It can’t be something that produces a lot of residue, which can gunk up the same system. And, of course, it needs to be flammable, (which is probably the easiest requirement).
Zip guns are also really easy to make. You can check youtube for some examples of those. Ammunition is the same. It won’t be commercial quality. But, if we’re talking about black market weapons and ammo, the production may very well be just as good. I think the Anarchist’s Cookbook has how to guides on all of the above examples, but I’ve never actually gotten around to reading it.
Hatchets and hand axes are unlikely to go anywhere. Sledgehammers and shovels are lethal as they are obvious.
I mentioned rebar earlier, but that stuff has some serious value as an improvised weapon. It’s small enough that it could, potentially, be stashed up someone’s sleeve, and it can easily kill.
I’ve always felt chain whips are a bit goofy, but you can certainly lash the hell out of someone with one. A whip can also be improvised from electrical cable, though, that’s more of a novelty weapon.
Tactical batons aren’t going to have disappeared either, and those are a lot harder to track down. Basically these are telescopic steel batons, they come in “18 and “24 varieties, and either size can really wreck your day. They collapse down into a small cylinder about the size of a pocket flashlight.
While I’m thinking about flashlights, any metal D-Cell flashlight can be turned into a really vicious weapon.
On the subject of dystopias, in general, I’d recommend researching feral cities and failed states. A lot of the feral city research has been in the last couple years, so getting access to good articles could be difficult, but there’s a pretty substantial body of work on failed states. This should give you some ideas for dystopias that range beyond: just another fascist state.