Fun fact: on an Android device, using the “OK Google” voice recognition, say “lumos” to turn on the flashlight. Say “nox” to turn it off.
The best Play Store one I’ve found is “Super-Bright LED Flashlight” by Surpax. Small ad on the bottom, the only thing I don’t like is that its easy to slip and change to mode to flashing or whatever. The other ones I’ve used have too many ads, including having to close an ad before you can even use it.