Butane stoves

The fastest and most versatile lifesaver for cooking in an emergency situation is a portable butane cooktop, the kind commonly used for car camping. Butane burns very clean, which will afford you more flexibility in how you provide the necessary ventilation, and more importantly, it burns hot and fast, meaning you can boil water and cook in a hurry, and soon be free to move on to dealing with other pressing issues in a grid-down situation.

I like these stoves so much that I keep two of them on hand, and store several cases of butane cans.

For added versatility, at little additional cost, you can get a dual-fuel version that will also connect to a 1 lb. propane canister. Some folks have reported that the propane burns better than butane when using the stove outdoors in very cold weather.