Nokia OZO Audio
This technology provided 360-degree spatial audio recording and playback.
(OnePlus 8 on the picture with OZO audio)
#Nokia

Variable Aperture
#Samsung

Privacy shade
Only show a small area of the screen for privacy.
#Blackberry

Screen SoundCasting
Technology that turns the entire screen into a speaker, enhancing audio output without traditional speaker grills.
#Vivo

Flexible shape
#LG

Smart cover
#LG

One-touch mirroring
#Sony

Hotknot
Is a Media Tek feature that lets two devices transfer data (like photos or contacts) by touching their screens together. It's like NFC but cheaper and less common, and mostly found on older phones.
DEMO
#Mediatek

Visualizer
#Sony

Center status bar clock
#OnePlus

Dual microSD
#Saygus

Notification pinning
#ASUS

Cyanogenmod Privacy Guard

EDIT: Early version of app ops
don't mistake it with Android 6 permissions

#Cyanogenmod

Gesture search
#Google

Z Launcher
#Nokia

HTC Sense Home widget
Smart homescreen panels based on your location.
#HTC