I've got an assortment, but I always come back to my USGI canteen kit. Inexpensive, durable, the perfect size to boil enough water for coffee and a meal, works on a stove or a campfire, easy to diy a lid and insulation, nests perfectly with the canteen and there's the bonus canteen stove. Love that thing so much that I've got one in all my kits, including my tackle box.