The Referee

The Referee can't be countered.
Whenever an opponent attempts to, says they
will, or does anything illegal or that they
otherwise cannot do in the format that you are playing, you may blow a whistle or make a
whistling noise by some other method. If you do,
you gain 4 life, draw a card, and add {u}. Then,
until end of turn, The Referee has "{u}{u}{u}:
Counter target spell."