I had a phone back in the day where all I had to do is violently flick it abruptly to enable the flashlight. I use my phone's flashlight a lot, always have.

There are apps that supposedly do the same thing, but I've never found one that worked so well, and so reliably as the one that was baked into the phone's features/OS/whatever. All the free ones I've tried have AIDS I mean ads, though it's been awhile since I last tried any.