Airdrop Card
The idea behind the airdrop card is similar to the Airlift card except that you can use it to attack enemy territories. This could be an over-powered card, so I would include two restrictions:
1) You can only use the card to attack territories you can see (this includes spy, recon and surveillance cards).
2) If you lose the attack, no armies are returned. The attacking force is either successful or wiped out completely.
This has the potential to radically change the nature of some games so I would set it to unlock around level 30. It wouldn't fit well in every game but I think it could be a fun way to shake things up.