The Cobett is the waterer of choice for winter time watering around here in situations where you can't afford to let an overflow run (rural water).  A bit pricey compared to the fountains mentioned elsewhere here but these waterers stand alone with no concrete and no electricity needed.  I installed 2 last fall and have been very impressed.  cobett.com  By the time you subtract the concrete and everything else, the waterers seem worth it especially since you don't have to worry about any valve freeze ups in "any" situation.

For tanks installed behind ponds with plenty of capacity for using an overflow/drain setup to keep water open, the used heavy constuction equipment tires with a piece of guard rail over the top for protecting the valve and drain seem to be unbeatable.