Lightning Overload

From wow.incgamers.com

Talent: Lightning Overload
Effect: Gives your Lightning Bolt and Chain Lightning spells a % chance to cast a second, identical spell on the same target at no additional cost.
Statistics: Rank 1 = 1%, Rank 2 = 2%, Rank 3 = 3%, Rank 4 = 4%, Rank 5 = 5%.