Yes - there is one.
I have to admit I was underwhelmed when IGG was revealed. Why would I waste a $5 buy on a copper, just to give the other guy a curse? Oh, I also get the ability to add -
more copper - to my deck? No thank you.
Now I don't claim that this setup was the only circumstance in which IGG is worth it (I got beat rather thoroughly by an IGG/Apprentice strategy), but in this game I think IGG was
the dominant strategy (I'll post the Councilroom link once its available).
Key characteristics of the Kingdom:
- Trashing for treasure cards, but for nothing else (Mint)
- Significant VP available for $5 hands (Duke)
- It also helped that I started $5/$2, so I could add a curse to my opponent's deck before his first reshuffle.

Here's how it played out:
- After opening IGG/- (should have been IGG/copper), I bought nothing but IGGs if I had $5+ or silvers otherwise. I handed out 8 curses this way, and fairly quickly.
- My initial plan was to dish out as many curses as I could, even at the expense of taking extra coppers if necessary, and then to quickly thin down with Mint (perhaps an early Mint would also have let me dish out curses faster).
- Then I realized that a theoretical deck with an infinite amount of copper would be fairly competitive at a Duke/Duchy race, especially if the opponent was bogged down in curses, so I used IGG's gain-copper ability every time I could. I wasn't diluting my deck, I was actually pushing it closer to the $1/card average I needed (it might actually have been higher at some points given the IGGs and a few silvers.
- At one point my opponent bought a Duchy, and fearing to lose the Duke/Duchy race I left the last two IGGs and plowed into the Duchy pile. Then the Duke pile. A couple times I had enough IGGs in my hand at one time to buy a Province with the extra coppers.
As I had planned, my deck was very reliable at getting one Duke or Duchy every turn. This Kingdom was very conducive to this type of slow-and-steady "tortoise" strategy. A different kingdom might have made a massive-final-turn "hare" strategy more feasible.
Of course I didn't play the strategy optimally - heck, I didn't even see it until a few turns in. And my opponent made a few misplays (usually trashing five coppers by buying Mint is a strong move, but not if the majority of your remaining deck at that point is curses).
I also wonder what other Kingdom would be similarly conducive to an IGG strategy. I never used Mint, but maybe I should have. Moneylender would be an alternate coin-only trasher. And I think Gardens may have been even stronger than Duke/Duchy (I very-nearly emptied the copper pile).
Thoughts?