This list is heavily inspired by
shark_bait's list.
I would like to present my top 10 cards beginners don't understand. What I mean by this is cards whose power level isn't immediately apparent. Even beginning players will understand the power of Goons to some extent (as they will likely love Militia) and King's Court (because Throne Room/Lab is already a superdupercombo!). This list tries to point out a lot of the more subtle cards, cards which tend to be overlooked by beginning players, but are a big part of expert players' arsenal.
I was a beginner once and scoffed at these cards. Why would anyone ever buy that card? Only after I learned more and more about the game I came to realize that those cards held a secret power, only unveiled to initiates. Most of the time the experience curve of such a card is as follows: From "it sucks!" to "it's overpowered!" to finally realizing when it's good and when it isn't.
Having a good understanding of these 10 cards will help you a lot with your game.
Enough meta-discussion, on with the list!
Honorable MentionsThese cards just missed my top 10, but maybe they would have made yours: Wharf, Duke, Menagerie and Fool's Gold
10. VineyardAt first it seems just a novelty, a card which gives VPs for action cards. It's much more than that. When you're playing any kind of engine, you will likely have a lot of action cards and the points from Vineyards can become enough on their own to beat a Province player. You need 18 action cards to make Vineyards worth as much as a single Province. That seems like a lot, but it really isn't. The upside of not needing any Provinces is that you're forcing your opponent to get all 8 which is quite hard to do. It's not uncommon for a Province player to take as long as 25 turns to drown the Province pile which gives a Vineyards player more than enough time to outrace him.
9. BridgeWhen I first encountered Bridge I thought it was just a Woodcutter trying to be cute. That's true to an extent, a single Bridge gives as much buying power as Silver. Its true strength is shown when playing multiple copies. It's a great feeling when you pull off KC-KC-Bridge-Bridge-Bridge for the first time to clear out the Province pile. Highway pales in comparison to Bridge, because it can't be KC'd and misses a +Buy. These things give Bridge the immense power it has.
8. Scrying PoolI remember playing against Scrying Pool players on Isotropic and thought other people were just wasting my time. How wrong I was. Scrying Pool is a killer card even without spying the opponent's deck. It's almost always a must-buy. Beginners tend to think it's just finicky and doesn't hold any real value (unlike Silver and Gold of course), but they will learn.
7. TacticianDiscarding cards and wasting turns is something beginners don't like to do. So why would they invest in Tactician? Well, because one good hand is usually better than two mediocre ones. It's much easier to do what you want to do if you start with 10 cards in your hand. Even money-based decks can benefit from a Tactician, since hitting $8 and getting a Province once is better than hitting $4 twice.
6. MasqueradeIntrigue was the first set I got and it had Masquerade. The card seemed fun for the interactive part of it, but nothing special. As I found out, it's actually one of the most powerful $3's in existence. Drawing before passing/trashing is a huge deal, it often allows you to get a decent card on the same turn you're trashing. There are cute combos and pins by playing a hand-reducing card first and anti-combos with Possession. Even without those card interactions, the card stands on its own.
5. StonemasonBeginners often won't look past the on-play card. "Trashing an expensive card? I don't think so!" The overpay part is actually what makes this card a hidden gem. A lot of $5+ cards are even better when you get more of them. Stonemason makes this easier. It seems so harmless as it only costs $2 on its own, but 2 $5+-cards and 1 Stonemason is just often better than just 1 $5-card.
4. ButcherAt first I thought it was just a glorified Salvager. Being able to just take the coins without trashing makes it a very good card and not that apparently powerful. I have found that Butcher just works in most decks, engines, BM, hybrids; I think I ignore it a teensy tiney percentage of games it appears in. Being able to save up those coins is very nice.
3. Black MarketAnother novelty card with a high impact on the game, I can't do it as much justice as Steff does, so just take a look at
his article. Needless to say, it has a lot of hidden power.
2. RebuildYou probably suspected it was on the list. I dismissed this card at first, thinking it would be weak. It was only after I discovered the wisdom of the F.Ds people I learned its true power. Being non-terminal is huge for a card like this. It just dominates most boards it's on and makes the game about finetuning its usage. It's so wordy that beginners might just skip it for the text, but what it does, it does brilliantly. I think it surprised a lot of advanced players as well, since it wasn't an obvious engine card enabling megaturns or something like that.
1. ChapelThis list wouldn't be complete without the granddaddy of cards "discovered" by evolving players. I remember when I looked it at and thought: That's only useful with Curses, why would I want to trash any Treasures or VP cards? Well, imagine that you could start with a fresh deck consisting only of cards you gained voluntarily (and Chapel). It's like using 10 Zaps to upgrade those pesky Coppers and Estates to Silvers and Duchies, but better! I'm preaching to the choir here, you all know Chapel's strength. Back then I didn't and a lot of beginners are still just discovering its power.