Sorry for taking so long. I was torn between several cards. Also, I was writing it up at work, and stuff happened...
So, about all of them, in alphabetical order (sorry for the lack of links, I'm rushing down right now).
Angry Mob:
Seems very good for 3$. I like the Villagers better than the Coffers variant, but removing Villagers still kind of feels like it should cost 4$ (assuming a roughly similar strength to Coffers, this is roughly Cutpurse levels). And you can even open two of these. Even if they collide, you steal more tokens from your opponents than you need to play both. Once an opponent's Villagers run out, this is 5$ material, too.
Arms Dealer:
This has the same issue most trash-from-hand attacks have: It helps your opponents most of the time. And if you ever manage to make them trash a good card, like by playing a Militia first, it can be really harsh. Also, yes, multiplayer is a thing.
Braggart:
It's fine, but I feel a non-attack version that makes you gain a card costing up to 6$, with each other player being allowed to gain a card costing 2$ or 3$ less, would be a better variant of this base idea.
Con Artist:
Much better with the changed wording, as now early hands with Coppers can actually block the attack. The fact that it doesn't hit players with 3 or more Coppers in hand also makes it unlikely to hit early, where replacing a card in hand with a Copper is most likely to help them. Still, it kind of bothers me that the attack is double-edged, after all.
Curfew:
You can't really skip this because of the huge bonus it gives, and the fact that the attack only harms users of the attack (unless there are much more expensive ways to use that token) makes it not really less mandatory. It's a bit too self-absorbed for my taste.
Cursed Tome
Love the flavor here, although arguably a Tome sounds like a Treasure. My main gripe here is that I think it would be more easy to trigger and less board dependent if it used a Cornucopia-esque "4 or more differently named cards in hand" to trigger cursing. Still a favourite from the start.
Demagogue:
Appears harsh at first, but people still have the option to choose. It follows a similar design idea as my Necromancer, without recycling the knights attack. Well, and Necromancer again is basically a Rogue variant. I'm not sure why I'm not really feeling this. It's a fine design.
Drunkard:
Bonus points for the originality. However, this is still a directed attack that only hits one player. It also delivers the revenge to the attack with itself, meaning it doesn't really provide a bonus to gain this.
Enforcer:
Another cute one. I originally was afraid the bonus was a bit too friendly when comparing the card to Legionary, but at the same time I feel that a 2 card hand is rather cruel. This isn't bad, but the brutality of the discard makes me feel it wouldn't be horribly much fun to play.
Extortionist:
A bigger Cutpurse. Not half bad. The only flaw this has is that it's a bit uninteresting compared to some other cards.
Frith Guild:
Fine. However, I feel this would be better if it made you discard to 4 either way. First, it allows getting rid of an Attack card to dodge further attacks, and also it would allow triggering Firth Guild itself.
Heretic:
Another one that seems kinda cool in principle, but it also looks a tad weak. Perhaps if it drew two to discard two, like Young Witch? Or if it was +2$, +1 Villager base for 5$. Terminal +1 Card is just really, really bad.
Infiltrator:
Also okay, but being a "fixed" Spy it doesn't seem overly interesting, and, like Spy, a tad too slow for a cantrip.
Land Dealer:
This is also perfectly fine, but another one that just didn't excite me much. And of course it's limited to only a few uses before it stops doing anything.
Mob:
I agree that this feels very oppressive, and the fact that playing BM allows you to dodge this completely doesn't make it better. I also don't like that this hits double if it hits. I'd probably like it more if it gave the attacked player a choice between trashing OR gaining a Ruins.
Negotiation:
A bit like a one-turn Embargo... I feel considering its cost and the fact that it might actually be so no other player even wanted to gain that card (and you can't block Victory cards) it's too weak. Also, it should probably say "At the start of your next turn" instead of "When you discard this from play". Not bad, anyhow.
Pretender:
I agree to the issue that often this won't feel like an attack. Sure, it sucks to play +Coin cards, but +Card cards become awesome. It also leads to issues if another player plays an Attack or a Throne Room + another Pretender. Like Braggart, I feel this would be better if it were a non-attack implementation of the core concept.
Regicide
This was one of the cards I was torn between. I like the novelty of the attack. My main worry was that it could lead to unpleasant experiences, because that kind of attack tends to whiff and if it doesn't, it feels really annoying to be hit by it. The first player advantage I think is mitigated a tad by the cost of 6$, but in general I'm not a huge fan of this kind of attack. Sorry, but that's the thing with jury decisions - they are very subjective. A grand submission anyhow.
Sorcerer:
I like this a lot! Obviously if one of the Hexes is Miserable, this is just a terminal Coffers very quickly. In fact, the actual bonus is a bit meh to me; Coffers are everywhere these days. Also, the base idea has been thrown around in the forums already (by you, perhaps?). So that's going against it... Apart from that, cool.
Stowaway
Glad you decided to put the attacking part in the current turn. It's a slightly more aggressive Haven/tactician, so my main gripe is that it doesn't feel terribly innovative. Otherwise it's neat.
Tax Collector:
This seems too brutal to me. I also believe that to make it it feel less brutal, you would have to change it in a way that would make it resemble other cards like Bridge Troll too much. Or, I gues, make it a one-shot? It's innovative, so that's a plus.
The finale was a triple between Regicide, Sorcerer and Cursed Tome.
The winner is Cursed Tome by GazBag. Congrats and thank you to everyone who participated.