Negate (Morningtide, 2008)

The quintessential blue spell. Countermagic is blue, creatures stuff is not blue. Countering a noncreature spell is just about the most blue thing one can do in the game of Magic: The Gathering. 

Negate is powerful and conditional at the same time, which is a sweet spot for establishing color identities and achieving a balanced game that is still dynamic and capable of supporting varied strategies. It is also self-controlling. The more negates are played, the worse negate becomes, because it can be targeted by the enemy negate.

Its peak value is in controlling cheaty non-creature strategies like big-spell ramp and combo. The mana value of 2 means it will always be better as a safety valve for fair decks than as an enabler of unfair decks. 

Its weakness, and all perfect card designs should have an obvious weakness (note: not flaw), is small aggressive creature permanents. This is a perfect summation of where blue should have a weakness as a color. Creature cards that generate value by virtue of being played early and sticking around (hence, "permanent") are too concrete and obtuse for the tactical and ephemeral style of blue to address efficiently.

Negate is not just a perfect design, I would probably put it at the top of best blue designs, period. If negate is the blue pillar of your format, then you have a format where blue gets to be blue, but non-blue decks don't suffer too much as a result of its unique access to interaction on the stack.

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