Minerva

{t}{u}{u}{u}; Minerva may assign 3 damage to six target creatures your opponent controls. (You may use only one of Minerva's abilities during your turn.)
{t}{x}; Deal {x} damage to target creature your opponent controls. {x} is the number {u} mana you tap to activate this ability. If target creature is not destroyed it becomes tapped until the end your turn.
Heads up! Brain freeze!