Sink

Once again based on observation of my own cats. They prefer their water to be moving, preferably fresh from the tap, and don't care what shapes they have to contort themselves into to get it. Cholmondeley used to sit in the sink opposite the toilet in my old house, and stare at you while you were trying to do your business until you turned the tap on.

I've now bought a pet fountain for my cats, which gives them the opportunity to drink from a moving aerated water source 24 hours a day. Highly recommended. See here:
http://www.amazon.co.uk/Pet-Mate-06039-Fountain/dp/B001NYGB8W/ref

Other pet fountains are available but I don't recommend the Cat-it, which is noisy and needs a lot of maintenance.