I sort of stumbled onto this the other day, and don't see any other posts explicitly mention it (maybe it just seems obvious to everyone else?).
The general idea is to open Ambassador/Ambassador, buying a Secret Chamber with the first $2 (which comes up often with this opening). Then try to keep the Secret Chamber constantly in play by sending it into the next hand, along with another card. That other card should be chosen strategically to try to line up Ambassador, 2xEstate/copper (either this hand or next), or simply to avoid an Ambassador collision. If the opponent has also opened Ambassador/Ambassador the likelihood of getting attacked every turn (and keeping the secret chamber in play) seems pretty good.
I haven't played more than 1 actual game trying explicitly for this combo, but it seemed to do okay in some sample games I played against a dummy opponent.
The obvious downside is that you are relying on the opponents attack to move the dead card (secret chamber) from your hand to replace it with either something to ambassador, or something useful for buying other cards. If they don't attack, secret chamber is another card that can conflict with the ambassadors, so usually it doesn't even get played for the discard for money option.
At worst it seems like the extra Secret Chamber buy early on won't hurt the deck terribly. At best it seems to remove a lot of unlucky draws from double Ambassador.
Any thoughts on this?