Let's say you're out in the wild, you've somehow been separated from your pack and you are left with only what you've got on your person. What features would you hope to find in that small flashlight you find yourself left with?

Is simple on/off functionality enough? How useful would different modes (e.g., flashing) be to you? Are you more concerned with durability, battery life, or something else?

I'm assuming here we are talking about small lights like the type you would find in a PSK, on a key-ring or on a neck lanyard.