With iOS 10, Apple added a ton of 3D Touch capabilities to your iPhone. For example, you can now press on alerts to view more information or press on an app's icon to view its respective widget. (If you own an iPhone 6S or newer, it has 3D Touch.)
There's plenty more, but perhaps none are as helpful as the ability to press on the flashlight icon in Control Center to adjust its brightness. The next time you need to use your iPhone's flashlight, slide up Control Center and instead of just tapping on the icon, press on it. You then have three brightness options: Bright Light, Medium Light or Low Light.
We briefly touched on this shortcut when iOS 10 launched, alongside other Control Center shortcuts for the calculator app (copies the last result), the clock app (starts a predefined timer) and the camera icon (gives you shooting options).