Beanie Babies, tulip bulbs, Pokémon cards, paintings, and gold have the advantage of being physically usable for something even if the sales market collapses.

Beanie Babies, tulip bulbs, Pokémon cards, paintings, and gold have the advantage of being physically usable for something even if the sales market collapses. NFTs tied to game items might potentially be usable as well even if they lose all collecting value. US dollars are generally considered a currency rather than an investment or collectable, but they are useful for paying taxes in the US if nothing else.