Grail means something different to everyone. When I hear “grail” my first thought is my most wanted card that I don’t own and is slightly out of reach for whatever reason - cost, scarcity, etc. While others may treat a grail as the centerpiece of their collection, and something they own.
My current grail that I’d love to eventually own is a PSA 10 Crystal Nidoking:
I’m so, so close to finishing my WOTC master set. I only need light arcanine, dark tyranitar, shining charizard; mewtwo, magikarp; holo ho-oh, and t17 typhlosion.
2009 4th grade illustration Arceus. Someday I’d like to own this card. Odds are my best chance of affording it would be if a PSA 6 or lower hits the pop report.