Yes, let's leave the iPhone users out. We may not be able to react to messages but we do have the greatest camera on earth.
The Google Pixel is one of the most photography-friendly phones out there, and that includes taking the quickest pictures on the fly. Even if the phone is locked, press the power button twice in order to turn on the camera, and then press the volume up or volume down button to take a picture.
Hit volume button.
Practice. Repeat. Practice makes perfect.
This trick will make you the quickest snap in the west. No, that snow leopard is not coming back.