I bought a light a few years ago that uses PWM to keep the light (LED) on at a minimum level all the time. This is so you can find it in the dark. Pushing the button cycles through Low, High, Strobe, Idle (minimum). It uses an Attiny85 running on a 9V battery. Specs say that it will sit in Idle mode, very low PWM, for up to 2 years on a 9V battery. Nice little light. Unfortunately, the website I bought it from is no longer online.