Here are the cards I like the best.
Usurer
Types: Action
Cost: $6
+1 Card. +1 Action. Reveal cards from your deck until you reveal a Treasure. Discard the rest. Trash the Treasure; gain a Treasure costing up to $3 more than it, putting it on top of your deck. Each other player may gain a Copper, putting it into his hand.
This is interesting. A nonterminal mine that draws the mined treasure if you've got two of them. Not sure how to gauge the power of this though.
Strong Room
Types: Action
Cost: $5
+4 Cards. +1 Action. You may return up to 4 VP tokens. Discard 4 cards, minus 1 card per VP token returned.
In games using this, at the beginning of each turn of the player who went first, each player gets +1 VP.
I like the "give up VP for a card in hand" mechanic, but one VP per card is a bit steep. This mechanic could be tweaked.
Metropolis
Types: Action
Cost: $7
+1 Card. +2 Actions. Treasure cards other than Copper produce an extra $1 this turn.
This could be bonkers with Silver gainers, but you'd need a source of +Buy for that kinda bonkering. I like the idea, not sure how much it'll change the game.
Stock Exchange
Types: Treasure
Cost: $7
Worth $2.
While this is in play, when you buy a Victory card, you may buy any number of VP tokens for $1 per token.
I actually really like this one. This could really mess with endgame conditions though. Perhaps tweak it by capping the number of VP tokens?
King's Greed
Types: Action
Cost: $10
Put your deck into your discard pile. Look through your discard pile and set aside up to 3 Action cards from it. Play them in any order.
I like this, and I'm not sure why.
Deed
Types: Treasure – Reaction
Cost: $5
Worth $2
When you gain a Victory card, you may discard this from your hand. If you do, +2 VP.
I like the idea. Interesting tradeoff: use the money or get the VP.
Philanthropist
Types: Action
Cost: $4
+3 VP. Each other player gains a card costing up to $5.
Interesting. To pile up the VP, you pump your opponents full of either (a) power $5s or (b) 3 VP of their own. Not sure if this will ever be worth it, but I'd like to try making it worth it.
Crown (B)
Types: Treasure
Cost: $7
Worth $4.
When you gain this, each other player gets +2 VP.
Interesting on-gain effect that interacts w/ prosperity. Plus, it is expensive and a $4 card.
Standard Bearer
Types: Action
Cost: $7
Trash this card. Put your deck (not including your discard pile) into your hand.
Feels like an easier Madman without the actions, maybe that makes it not as easy, and thus, more balanced than at first blush. I love Madman.
Savant
Types: Action
Cost: $6
+3 Cards. +1 Action. Each other player draws a card, then reveals and discards one or more cards. He gets +1 VP per Action or Treasure card he discards.
This is interesting. I like the VP interaction, but it may need to be tamed.
Queen's Palace
Types: Treasure
Cost: $7
You may choose a Treasure card in your hand. Play it three times.
Interesting. Decent. Fun enough. Thematic.
Hedge Fund
Types: Action
Cost: $5
+1 Action.
You may return a VP token. If you do, +3 Cards, +1 Buy, and each other player gets +1 VP.
Setup: Each player gets +2 VP.
I like this mechanic. As some others have mentioned, this could do with a +1 VP cost. In any event, I'm a big fan of the VP for stuff idea. Maybe that's broken, but it is cool.
Palladium
Types: Treasure
Cost: $7
Worth $4. +1 Buy. When you play this, trash all Treasures you have in play. +1 VP for each card trashed.
As it reads, this trashes itself. Seems like a special type of deck that would work with this. Maybe a deck that wants no treasure and has lots of synthetic money. In this case, Palladium will be an uber deck thinner that has a one-shot economy boost and non clogging VP. Intriguing. Not sure about the balance of powers.
Smelter
Types: Action
Cost: $6
Reveal cards from your deck until you reveal an Action card, a Treasure card, and a Victory card. Trash an Action card, a Treasure card, and a Victory card from the revealed cards. If you do, gain 3 Golds.
Living dangerously. I think it would be fun to see how this plays out. Great way to combat Ruins. Interesting that you'll (with some probability) have choices about what to trash for some types, but never all types.