Water Containers

Platypus makes ultralight soft-sided plastic water bottles. They are one-sixth(!) the weight of a traditional lexan/Nalgene bottle (.9 oz for a 1L, 1.3 oz for a 2.4L); they are durable enough to last months on the trail; they are collapsible, so they do not consume any space in my pack when not in use; and they make great pillows at night when (mostly) filled with air or water.