The Vargo Titanium Bot works as both water bottle and a cooking pot. The screw-on lid has a silicon seal to make it water tight. When cooking, place the lid on upside down.

This is the newer version, with graduated markers, running from 300ml to 900ml, in 100ml increments. On my scale, the weights are 138g (4.9 oz) with lid, 96g (3.4 oz) without. This compares well to 900-1000ml pots from Evernew, Toaks, etc., and could mean you can leave a second water bottle at home.

Included, but not pictured:

• Reflectix cozy (~0.5 oz), homemade. Keeps the contents hot, and prevents you from burning your hands.
• GSI microgribber (0.5 oz). Works pretty well, but beware of steam as you lift the pot.