Shift clicking a stacked item (2 or more) into an enchantment table will clear all NBT data from the item that goes into the enchantment table.  For example if you take a stack of 2 arrows of slowness and shift click it in an enchantment table the item in the table will become an uncraftable arrow with no effects, works with anything with NBT data. (tested Banners, Arrows, Potions)