AKA Holding out for a hero.
Where did the hero card start I wonder, The most obvious application, and the only one as a permanent game mechanic as far as I know is in World of Warcraft. If you've seen it going then you'll know that outside of the deck there's a hero card, sometimes oversized, which changes the way individuals play the game. Actually now that I think of it the Harry Potter TCG had that before WoW came out. Extra points to HP for having those cards be actual holograms rather than just shiny cards. Either way a change of hero is a fundamental change in play style and a great way to reflect an individual play style. They did something similar in MTG, I think it's in a style called EDH, but I'm not entirely sure how it works as I've never played it for myself. I hear the deck style has to play into how your general actually works, which is a good restriction to have in a game with so many cards and styles.