Since losing life isnt all that uncommon, Rowan, Scion of War can frequently discount your spells by at least a few mana
This Knight finishes games for you by skipping your attackers right past all those moderately-weakened creatures you werent able to finish off
It's got a strong possibility of seeing play in Standard, and is sure to become a heavily played card in Commander, too, given its cheap cost but high utility
Note that I left out some cards designed purely for multiplayer formats, so they would skew the history
And if they kill it, you get to draw an extra card
(If it prevented all damage, a la Dawn Elemental, it would be my number-two card, but there is no way it knocks out the best one.) #2 Strionic Resonator Sometimes, we get these quirky little Johnny cards that you just know are going to be fun, such as Rings of Brighthearth