Dark Simulacrum

Dark Simulacrum is a death knight PvP talent, available at level 20. It applies a debuff to an enemy player that allows the death knight to copy the target's next spell cast and unleash it.

Unlike Spell Reflection, Dark Simulacrum does not cancel the incoming spell. In general, if you can't reflect an ability, you won't be able to copy it either.

Trivia

 * This ability was mentioned in the April Fools' Day patch 6.1.4 Evil Patch Notes: "Dark Simulacrum is now 37% easier to pronounce."