Stolen Identity (GTC) from Gatecrash, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Clint Cearley
• Card Text:
  Put a token onto the battlefield that's a copy of target artifact or creature.
  Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)