They are common in certain Magic: The Gathering promotional cards, Yu-Gi-Oh
Kimahri, Valiant Guardian* Essentially a 4/4 for 4, Kimahris ability to copy your opponents creatures, and tap one down while keeping its vigilance gives him an interesting role to play in some Commander decks
If a card requires you to discard your entire hand and draw new cards (such as Windfall), Psychosis Crawler will not die since state-based actions aren't checked until the spell finishes resolving, and you'll have a hand of cards once it does, keeping Psychosis Crawler alive
This allows you to put two damage counters on any of your opponent's Pokemon when it moves from the Bench to the Active Spot
If an expertise spell allows you to cast a split card, you may cast either half or, if that split card has fuse, both halves
And speaking of making copies, Psionic RitualPsionic Ritual can be like the instant/sorcery version of Rise of the Dark RealmsRise of the Dark Realms if youve got enough Horrors, or even just a bunch of creatures and a Maskwood NexusMaskwood Nexus, and some full graveyards
