For warm-weather canteens, I use clear PETE soda-pop bottles. Light, tough, recyclable and free. They can be used to purify drinking water, too. Set them in the sun for a day, and UV radiation will kill biological pathogens. Simpler and better tasting than bleach, iodine or boiling.
For winter, though, I like uninsulated metal canteens that can be set near a fire to warm water or melt snow*. (*Make sure the cap is loosened so steam can escape.) I came across these Italian military surplus six-liter olive oil containers that are perfect for the job. Heavy-duty aluminum with a two-piece spout. A large opening for filling and a small one for pouring. Both caps are attached with chains so you won't lose them in the snow. (I've lost a lot of things in the snow, up to and including a tent...) There's a bale for carrying, and one side is concave so they don't bump into your legs like round buckets do. The opposite convex side has a couple welded brackets that will facilitate strapping to a pack or sled.
They came with a button-on wool cover. I'm not sure what the cover's purpose is, other than to look cool and make handling more comfortable in freezing weather. Perhaps the insulation moderates temperature swings and helps olive oil store better. Or it's intended to be wetted for an evaporative cooling effect in hot weather. Or all of the above.
It occurs to me that when set around a fire, these tall cans would not only warm water, but also reflect heat. (Again, make sure the cap's not on tight, or you're building a bomb.) I'll test that theory in a couple weeks when deer season starts.
On the internet, these are available for $32 at Sportsman's Guide, and $79 at Deutsche Optik. Guess it pays to shop around.