Looking at my rankings, I find myself thinking "what was I thinking?" more often than not. In particular, I put Mining Village, Bishop, and Envoy at 50-48. I have no idea why I did this. Maybe it was a typo or a misclick, given my lack of familiarity with this system. I think that, in the end, I probably should have had Smithy, Militia, and Throne Room higher than I did. But here are the differences I WILL defend:
Mission at 12. Attacks, trashing, and gaining are all very straightforward and useful things you can do on your turn which require no buy of any kind. If you are trying to win an Ambassador war, or are trying to use Travelers, or rip through your enemy with Knights, or are buying mostly Events anyway, or have Horn of Plenty... any one of these things can make Mission a monster. It is "niche" in the same way that Procession is "niche." When it's good, it's insane, and you should always look for ways to exploit it when it's there. When you take the time to look, it's more common than you might think.
Quarry at 8. Before Adventures, this was my favorite card in Dominion. It's a Gold for the cards that engine builders most want to buy, and even more astonishing when multiple buys are involved. Cost Reduction isn't just for a last-turn megaturn: it helps the midgame just as much. Thankfully, I'm not alone on this one.
I had Magpie at #1. Like Ironmonger and Tournament, it is something of a Peddler +. It loses the ability to act as a Peddler under certain circumstances, like when the wrong card is revealed or your opponent has a Province, but it has side-perks to balance it out. And although Ironmonger and Tournament have VERY nice side-perks, Magpie is arguably better than either.
On to Villages. I actually consider Mining Village worse than Walled Village, because I use the bonus from it so rarely. And on the other end, strange as it sounds, I think the best village by FAR is Port. Wandering Minstrel is incredible, but it still can't touch Port.Imagine a card that costs 4 and reads "+1 Card, +3 Actions." That fictional card may sound obscenely strong compared to other villages; enough to render them obsolete. Port is even better than that, because having the extra actions distributed moderately across your deck lines them up better with any terminal draw you have. Although the perks are nice, we get villages first and foremost for actions. Port has the other villages solidly beaten on that front. Any issue it has as a major cog of your engine is that the pile empties so quickly, which is arguably in favor of Port, not against it.
Finally, we all severely underestimated gainers. Like, terribly underestimated them. Gain-and-play shenanigans are just too good to pass up, and they make heavy trashing a little safer because you no longer need as much cash around to build back up. I regard Workshop as a middle-of the road 3 cost. But the 4 cost trashers are something else. I have Armory at 30. If you track your deck, it can give you exactly what your next hand will need exactly when you need it. I have Ironworks at 14. That single extra action does incredible things to gain-and-play tricks. And the final gainer barely plays like a normal "gainer" at all. It doesn't allow you to trash away all of your economy safely like the others, and it doesn't facilitate gain-and-play. Still, I feel little guilt over having Duplicate - yes, Duplicate - at number 3. In a fully functioning engine, Duplicate is almost impossible to describe. Getting an extra copy or four of the best card you buy that turn feels less like playing with a normal gainer and more like playing with a Haggler or a Horn of Plenty. Unlike those cards, however, you can always open with Duplicate. Being able to save it on the Tavern mat until you get the juiciest prize possible is just icing on the cake. I'm calling it here: Duplicate is the most egregiously underrated card in the rankings this year.