Just Light is the most basic flashlight.

I needed a flashlight app that did nothing else but shine white light. Almost every night, I use my iPhone as a reading light and, with other flashlight apps, I was accidentally changing the color or starting disco strobe mode. I tried holding just the edge so as not to touch the screen, but my fingers would always reach around and turn something on.

Just Light has almost no features, just a solid white screen with idle shutoff disabled, so the light shines until you turn it off.