Sneaky Pickpocket

{u}{b}, {t}: Target opponent exiles a card from his
or her hand. Until end of turn, you may play that card. If you don't, create a colorless Treasure artifact token with "{t}, Sacrifice this artifact:
Add one mana of any color to your mana pool." Activate this ability only any time you could cast
a sorcery.
"When it comes in handy, fine, let's keep it. If not,
let's just sell it for some treasure!"