Boreal Crate

Every crate hands over one item from the Frozen Chest pool, and by the point you can fish these you have outgrown most of that list. The Ice Blade, the Ice Boomerang and the Snowball Cannon are all pre-Hardmode weapons you will never put in a hotbar again.

Ice Skates and Blizzard in a Bottle are why you keep opening them. The skates feed Frostspark Boots, which plenty of players wear until the endgame, and the bottle is one of the four balloons the Bundle of Balloons needs. If you rushed past the Ice biome earlier and are now short one link in either chain, fishing a frozen pond beats hunting chests.

The Fish shows up here far more readily than in the chests it normally sits in. It is a curiosity rather than a tool, so it only matters if you are completing the item list, but this is by some distance the easier way to get one.