Have there been any Meta cards that use rules outside the game? Obviously it wouldn't be tournament elegable,but something cool like a:
2/2 'god like' knight card that has every passive ability possible to make him untouchable or with an ability that almost guarantees the owner wins in a matter of turns, but successfully wining with that card in play means your opponent now own that card.
That sounds like something you'd find in one of the Unglued or Unhinged sets. They did card-ownership stuff with 'ante' back in the early days, but card values and the random nature of losing them nullified it.