Pur 3 Stage Horizontal Mount Faucet Water Filter by Procter & Gamble
This water filter wins our vote because, unlike the rest, it clicks onto your faucet without major tools. The filter purifies about 100 gallons of drinking water before it needs changing, and a red light tells you when to do that. The whole thing swivels 360 degrees to fill pots and easily switches over to unfiltered water for washing them.
About $40, filter included; purwater.com