Rainwater tanks collect and store rainwater to feed gardens, wash livestock, and kill wicked witches. Harvest rainwater to free flying monkeys with today's Groupon: for $450, you get three Rainwater Hog modular tanks from Rainwater Hog (a $900 value).

Three Rainwater Hog modular rainwater tanks guzzle gutter gushes via downspout straws, storing up 50 gallons of H2O in each sturdy stomach. Attached to a vertical wall with a wall kit or tucked horizontally underneath a deck or patio, the tanks can be strung together by threaded connector tubes—which come with each unit purchased—so all three fill simultaneously. Additional tanks can be added easily to start a water-collecting conga line.

Each tank is lined with durable quarter-inch-thick walls that are primed with UV additives for extra weather resistance, and tanks can last more than 20 years with proper care. Once installed, homeowners can hook a hose up to three tanks to irrigate a garden, wash a car, flush a toilet, or transform an unfriendly neighbor's ornamental rock garden into a fishless fish tank.