Jester's Cap: This card's power is directly proportional to the power of your opponent's deck. Even against a deck full of chaff, it can remove the most dangerous cards. Against a tournament deck, you can cripple the opponent by removing win conditions or key removal spells. With a little mana acceleration, I find it a potent weapon against even cut-throat decks. And it's a card that's full of options. Some choices will always be better than others, but Jester's Cap is one of the only cards in Ice Age that really requires brainpower to use optimally while simultaneously being versatile enough to use in most situations (Necropotence is very much that way, but I don't think I could convince even KJ that Necropotence is casual...). And let's not forget that Jester's Cap comes with a bonus: you can recur it and eat all the good cards out of your opponent's library.