bulbasaur full art pokemon card (フシギダネ) 166/165 Grass Leech Seed (20) Heal 10 damage from this Pokémon. Bulbasaur (A1-227) — Pokémon TCG

The most notable on the list is The One Ring from The Lord of the Rings: Tales of Middle-earth , the infamous card that only has one copy in existence

Thats thanks to the Powerstone-aping Vibranium artifacts, which cant be destroyed and can tap for artifact spells

Even attaching Skullclamp to a larger creature is often worthwhile, as killing said creature will be risky for the opponents who don't want you to reap additional rewards.

Who cast them

If Mishra's Foundry becomes a creature and you haven't controlled it continuously since the beginning of your most recent turn, you won't be able to activate its first or last abilities, and it won't be able to attack (unless it somehow gains haste)