Phễu Làm Nguội Trứng Luộc

If you boil an egg, when done they are hot and need cooling.  If you just put them in a cold container of water they cool slowly as the water close to the egg heats up.  The best way to cool an egg is via running water but if you leave an egg under a running tap it'll use a lot of water.

This funnel allows you to put the eggs in a 'pint glass' and feed cold water into the bottom of the glass, this forces the warmer water to overflow the top of the glass.  This gives you running water but wastes a lot less.

It will probably not be useful to anyone, but you never know.