Combo: Ironworks and Great Hall
|Ironworks / Great Hall|
Due to Great Hall's typing, when it is gained via Ironworks, the player receives +1 Card and +1 Action, turning Ironworks into a cantrip. Since Great Hall is also a pure cantrip, essentially "invisible" in your deck (barring handsize attacks), this is a lot like playing a cantrip Monument, without the + . However, since the Great Hall pile has only 8 cards in a 2-player game, it makes Ironworks into a cantrip Monument that only works at most 8 times, usually fewer. And once that pile is empty, you now just have a deck full of mostly useless cards, leaving you far behind any player that actually invested in economy, even if they only gained Silvers. The extra from your Great Halls will almost never be enough to make up for losing the Province split. As such, while this interaction can be useful in breaking a tie, it is most often a distraction.
This interaction has the almost unique quality of being improved by Scout; if all three cards are in the kingdom, Ironworks can be used to gain Great Halls, which Scout can then draw into hand, turning Scout into powerful non-terminal draw.
On boards on which Ironworks is a good buy anyway, for gaining engine components, Great Hall can make a good target for Ironworks after you've already gained most of the engine components you need and built your economy.