This list doesnt include cards that make temporary copies that leave play at the end of the turn like Kiki-Jiki, Mirror Breaker or Flameshadow Conjuring
As long as you're using mana rocks or Treasure as your mana sources, Shadow can significantly reduce the mental load of playing Magic , since you rarely need to worry about your opponents responding to your spells
They are still creatures, sorceries, artifacts, etc
Finally, you harmonize Nature's Rhythm to find The Jolly Balloon Man, who copies Nurturing Pixie
Or...you can just attack and spend three mana to turn it into a +X/-X where X is your Island count, so this can win very quickly
It immediately spiked from $10 to nearly $50, but we are now seeing the inevitable unban cooling effect