I played a very interesting game recently where we loaded up the kingdom cards with treasures and topped it off with a few cards that act on treasures.
Thief
Mine
Mint
Loan
Talisman
Venture
Royal Seal
Contraband
Harem
Bank
(with Platinum and Colony)
The effect was very interesting: Thief and Mine, both normally weak, suddenly became must-buys. While trashing is possible via two cards (Loan and in the purchase of Mint), it's very limited, so the risk of clashing terminals in this +actionless deck wasn't so much of a big deal.
With all the treasure around, Thief was very powerful, and Mine had a lot more options than it usually gets. In particular, Mining things to Harems (and, similarly, Minting them) was important for the VP count.
But the defining aspect of the game was somewhat unexpected, at least to me: we ramped up wealth so fast and so dramatically that we were buying colonies in no time and wasting money anyhow. So +buys were critical -- yet, the only source of +buys is the Contraband, which allows a player to name a card they can't buy. These decisions were sometimes tricky. Do I name Colony, guessing that my opponent might have treasure still in hadn to have bought one otherwise? Or do I risk he's only got 10 and name Province? Sometimes multiple Contrabands were played, allowing a shut-out of both piles.
Contraband doesn't normally get a lot of play (at least not in the games I play), so it was very interesting to see it suddenly become the focal point of a whole game.