Dark Simulacrum

Dark Simulacrum is a death knight ability, learned at level 85 for. It was first announced in the Cataclysm death knight preview.

The death knight strikes a target, applying a debuff that allows the death knight to copy the opponent'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.