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Obviously these may be a miss for your format for other reasons (power, archetype mismatch, rarity, don't run planeswalkers etc) but here's a few that I found interesting, divided by broad category rather than color: While I'm still not done reading Cosima, God of the Voyage (I'm on chapter 2, the language is a bit dense) these cards are ones I do like both sides of

Mardu commanders like Ghen, Arcanum Weaver, Jirina Kudro, and Jan Jansen offer unique abilities and strategies, from enchantment recursion to token generation and sacrifice effects

Kassandra, Eagle Bearers Assassin typing also makes it a viable addition to Assassin kindred decks led by Altar Ibn-LaAhad and Ezio Auditore da Firenze

So, if your opponent wants to Summon a monster or activate a Spell, you can negate it as long as you have the right Counter Trap face down

If you create a land version of either with Yue and a Clone, you can have it exile itself on entry, before returning as a Clone again to repeat the loop

Conjure is an Arena-focused mechanic that automatically creates copies of specific cards to add to your library