Everywhere. I mean literally everywhere, even on the plane.

While I've not used it in an actual life or death situation, I have used it for a number of interesting things like stopping a moonbounce full of kids to retrieve my three-year old who had been bopped in the nose and I needed to get the other kids to stop jumping so I could get in and grab my kid.

We've also used it at impromptu games of soccer to referee, and we were at a festival and there were various races (sack race, 3-legged race) and it was fun to become the race-starter.

But I carry it mostly for the NYC factor. Three things I think I need in NYC if I survive the initial blast - a way to signal rescuers, a bandanna to cover my face to lower the risk of long-term illness from the dust, a light to see my way, and some water to drink and keep my bandanna wet. All of this is on my person all the time, everywhere except in the shower and in the swimming pool.