Im not going to make a point to do this for every color, but there is one card that is technically white that overwhelmingly makes most Cubes, yet it doesnt feel quite right to give a white slot to today
Guardian Project In any singleton format like EDH, Guardian Project reads cast a creature spell and draw a card. Any creature
Here's a full list of the different rarities and how many times each got printed (Source): U2 20.700 U3 31.000 U4 41.300 C1 31.000 C2 62.000 C3 93.000 C4 124.000 C5 155.000 C11 341.000 Examples for U2 cards from Arabian Nights are: Drop of Honey, Serendib Efreet and Juzam Djinn
Much like Ruhan, Wyll, Blade of Frontiers makes for an interesting Voltron-Commander with a chaotic wrinkle to build around
While Mono-Black decks have access to a lot of top-tier graveyard hate, including the inimitable Dauthi Voidwalker, Mono-Blue decks, or blue decks without black in their identity, arent quite so lucky