Rocket stoves are in my opinion, the absolute best prepper stove available today. They use multiple fuels, and if you use wood, they use about 5% (or less) of the wood it would take on an open fire. When properly stoked, they boil water rapidly, and can cook big meals. A single 2×4 could cook many meals, Because the concentrated flame hits the bottom of the pan they cook fast, (over 500 degrees F) yet the flame can be adjusted with the fuel size and quantity. They are beginning to get popular, and there a several stoves now available. The biggest problem I have heard of has been is addressed in this video.