My favorite water bottle is the Camelbak Chute Mag (I use both the double-wall insulated and more standard "nalgene" variety). The cap lid is easy to use, and the magnet keeps it open while you're drinking. Bets of all, it's a large enough spout that you can chug some water (I never drink enough water if I have to use a straw). The handle is also comfortable for carrying it for extended periods of time, and makes it easy to clip to a pack with a carabiner. While we're traveling abroad in places where the water quality might be suspect, we also use a Lifestraw water bottle. If I'm backpacking or hiking, I sometimes use a Smartwater bottle, or an old school widemouth Nalgene that fits my water filter.