Woot Wine ships their wine packages with these frozen “ketchup packets” full of water in them to keep the wines cool during shipment. They always suggest reusing them, but I never figured out why.
Tonight I figured out that they make an excellent reusable “ice cube” for whiskeys and scotches. Unlike normal cubes, they don’t water down your drink when they melt.
A friend of mine spent a good amount of money for a similar (but more elegant) solution for her father, involving cubes of granite that one would freeze and then put in their glasses of expensive scotch.