Set Live Photos as your lock-screen wallpaper
Another cool feature that rolled out with the iPhone 6s is the ability to shoot and watch Live Photos, which are just like still photos except that they capture 1.5 seconds of a low-frame-rate "video" on either end when you press the shutter. You can also set one as your wallpaper, and get it to move via 3D Touch by pressing down on it from the lock screen.
Activate the app switcher
As you no doubt know, a double-tap of the Home button launches a gallery of open apps so you can freely shuffle between ones you’re using simultaneously. But for the more advanced among us, there’s a 3D Touch trick that does the exact same thing. A hard press of the far left of the display launches the app switcher, too.