I'd like to do things with prizes: my favourite would be to play with them as they were bad things:
So salvager a prize (other than princess) because you desperately need this buy
Or apprentice a prize (not Trusty Steed or Bag of Gold) because you have to buy the last peddlers to three-pile or enable your conspirator-chain
Discard one with sc, vault, cellar, storeromm, because you need another card/1 more coin
Bishop a prize to get 1VP and win
Trash a prize with a must-trash card (trade route) to get the huge amount of $ of them
Pass a prize to your opponent because of Masquerade
Of course, situations where this is good play will be rare, but still there will be some edge cases you actually want do that