Last summer, July was one of the hottest on record, and coincidentally my family happened to come into possession of a Dyson Hot + Cool Air Multiplying Fan. Originally, we were more enamoured with the vacuum we obtained at the same time and the fan just sort of sat there, but as the heat continued to make our home into a sweat lodge the fan was plugged in and our lives were changed. Cool breezes prevailed against the heat, and the quiet, gentle cooling effect made our home habitable again.
In the winter, this fan proves even more indispensable, it can actually heat our main floor in less time than either the gas fireplace or the electric heat, and it's so portable we even take it to the cabin up in Whistler. Like all Dyson products, it's a bit expensive, but worth every single penny - you'll save more in electricity in a year than it costs to buy, so it's a great investment.