Invisibility cloak\n\n All are very rare and expensive. In Fantastic Beasts and Where to Find Them it is said invisibility cloaks may be spun from pelts of the Demiguise. Invisibility cloaks can also be ordinary cloaks with a Disillusionment Charm or a Bedazzlement Hex placed on them.
"Holo-portraits premium", (colloquially "holofoil") are the most rare and the most valuable of all types of cards. These cards are only available for "character" cards, which have the portrait of the character on them (origin of name).