Ice Spear

Ice Spear is a polearm. It inflicts ice-based damage onto targets and is thus more effective to enemies with a weakness to ice-based attacks.

Source
Ice Spear can be purchased from the Culless Munitions in Lestallum, the Verinas Mart in Ravatogh, and the Imperial vendor outside Steyliff Grove during Chapter 7 for 1,500 gil. It can be sold back to shops for 750 gil.