Ice Feather

Ice Golems only walk out during a blizzard, so you need Hardmode plus weather, and then you need to be standing on the snow surface while it blows. The golem itself is slow and telegraphs everything, so the fight is easy and the waiting is the hard part. If the storm clears before the drop lands, go do something else and come back the next time it rains up there.

The only thing it builds is Frozen Wings, a decent mid Hardmode pair that most players replace within a few hours. Craft the wings even if you already fly better, because the finished item is worth several times what the loose parts fetch at a shop.