A flint rod with a wheel striker instead of a loose steel — the mechanism from a lighter, without the fuel.

The advantage is one-handed operation and a consistent spark every time. Scraping a rod with a separate striker takes two hands and some technique; a wheel just works, including with cold hands or gloves on.

That matters more than it sounds. Fine motor control is the first thing to go when you are cold, and that is exactly when you need a fire.

No fuel, nothing to evaporate, works wet.