Fire gels are great. There's a great number of other flamable items you can cook with too. I once, for a challenge, made lamps of bacon grease and used that to cook bacon and eggs. The same tricks work with almost any kind of fat or oil. I'd do that in a power out situation - but if it was SHTF then I'd be saving the fats/oils to eat.
You can also cook on candles - but you either need a bunch of them to get it hot enough or you need to turbo charge the wicks (try corrugated card with the corrugations running upwards).