Buggy Code

X is half the converted manna cost of the target creature (round down).
When enchanted creature activates an activated ability or is declared an attacker or defender flip a coin, if heads play continues as usual, if tails the player who cast Buggy Code gets to choose the target of the activated ability or attack, if the creature was declared a defender it instead taps.

The curse of buggy code is quite possibly the worst that could befall a programmer