This is a top pick of many for a lot of different reasons. Google Play does not give it a great rating, but if you need a flashlight app, you should definitely try it out. It is minimal, without a lot of extras, but it is also elegant and contains everything you need.
There is a widget for the home screen and functions quite like a switch. Once you turn it on, it will not turn off even if your home screen does.
Some other features you might be interested in are the screen illuminator, the timer that has an auto-shutoff and even strobe light effect. It is both stable and lightweight and works great on your Android device. It may not be a famous name on the current market, but you can install it and use it for years to come.