yugioh card celtic guardian Yu-Gi-Oh - YGLD-ENA09 - 1st Edition This is of Ultra Rare rarity Buy Your Yu-Gi-Oh! Celtic Guardian

You can only use this effect of "Valkyrie Funfte" once per turn

Riffles Method

8 25th Anniversary Celebrity Collaborator Cards are Unique Pokmon Cards with Star Power Copies: 3 Pokmon 25th Anniversary Celebrations Though the appeal of these cards may be very different from the rarest versions of the most iconic cards in major TCGs, there's no overestimating how rare they are

These are incredibly difficult to pull, and are currently going for about $2,000 apiece on TCGplayer

Additionally, Hauntwoods Shrieker has a two-mana turn face up ability to get the creatures face up cheaper than most mana costs you would be paying