The BFM (Big Furry Monster) from Unglued is two separate cards, where the title and mana cost are so large that they need to be divided...
And from the very first set, Arabian Nights, Shahrazad requires both players to pause the current game and start up a new subgame beside it, with the loser losing half their life points. Just like in the original 1001 Arabian Nights collection of folk tales, the card can be played again and again in those subgames to keep the story going...
I like Netrunner's Scorched Earth, the card where you stop playing "try and catch the hacker breaking into your Corp" and just blow them up. It's rather elegant in its simplicity.
