My card was Barrister (and Claim). I knew a trashing attack would be a tough sell, but I wasn't expecting zero votes.
Barrister
Types: Action Attack
Cost: $5
+2 Cards. Each player (including you) reveals the top 2 cards of his deck; you may choose a revealed Treasure for him to trash. He discards the rest. You may gain a Treasure from the trash.
Setup: Replace one of each player's starting Coppers with a Claim.
Claim
Types: Treasure
Cost: $0
Worth $1. When you play this, look through your discard pile. You may trash a Claim from your discard pile or hand. If you do, gain a Gold, putting it into your hand.
Clarification: In a 6-player game, the starting player does not replace a Copper with a Claim.
Anyhow, as I mentioned in a previous thread, this wasn't a bona-fide submission, and I would have disqualified it had it won. It's actually for my expansion, Enterprise, where there is enough room for 6 copies of Claim. I submitted it to this contest for feedback because it seemed to fit the expansion (trashing Attack, starting deck change, gaining from the trash).
First of all, I want it to be known that I have nothing against Lawyers; I do not think they are all thieves. The card's pre-Guilds name was Tax Collector. Once Taxman was revealed, I needed another name that would work with the get-other-players'-Claims mechanic. "Historian" didn't sound Dominion-y to me. I had it named "Assessor" for a while, but I really didn't love that name either. Eventually I hit upon "Barrister" and went with it. I think it sounds more Dominion-y than "Lawyer", but that could just be because I live in the U.S. where "Barrister" isn't really in the vernacular.
As for the card itself
One day I hit upon a cool twist for a trashing attack: trying to get a card that you could only find in other players' decks. The smoothest way to make this happen was to have a Copper replacement that you needed two of to activate. Unfortunately, this naturally led to at Thief-like card, so already it's scoring low on the popularity ladder. Do you have any idea how hard it is to make a Thief variant that costs $4 and isn't strictly better than Thief? Noble Brigand should give you some idea. To differentiate it, I decided to make it cost $5 and beef it up a little. Unfortunately, this just led to everyone calling it a "Super-Thief".
The card has to be able to get any Treasure from the trash, rather than just the ones it trashed itself. Otherwise your opponents could just be all, "I just Upgraded my Claim, lolz, try to steal it now." Here's something nobody noticed: unlike Thief, Barrister can only gain a single card per play, even in a game with more than 2 players. So it's not really strictly better than Thief, even at $5.
Aaaaaanyhow, the version I have printed out has the +2 Cards, but doesn't allow you to trash your own Treasures and doesn't allow you to choose not to trash your opponent's Treasures. So it's even closer to Thief. Luckily this contest wasn't a total bust for Barrister in terms of feedback. WanderingWinder's analysis has convinced me that +2 Cards is too strong. I believe I'll try this version next:
Barrister
Types: Action
Cost: $5
+$2. Each other player reveals the top 2 cards of his deck; you may choose a revealed Treasure for him to trash. He discards the rest. You may gain a Treasure from the trash.
+$2 instead of +2 Cards makes it less easy to build an engine that just spams Barristers. It might still be too strong, but hopefully not.
As for Claim, I was surprised to hear many people say that it wouldn't be worth gaining another "Copper". That seems ridiculous. If you already have a Claim and gain a second one, that second one is basically a Gold. Heck, if you have one Claim in your hand when you steal the other one, that's pretty much a free Gold (in your hand!) right there. That seems worth it to me. If you don't think stealing Gold with Thief is worth it, then I don't know what to tell you.
Anyhow, thanks to everybody who gave feedback on the card. At this point I'm honestly considering scrapping it from Enterprise, but I'm not sure yet. Some people like the concept and some just didn't think it belonged in Dark Ages, which is totally fine. It would be nice to have a trashing attack in my set and I haven't thought of a better one yet, so I'm on the fence.