Erase data without internal storage
#OnePlus

Speaker ONLY inside USB C hole
#Huawei

Dual display
Cameras are only on one side so you can enjoy notchless display.
#Vivo

Glove mode
#Sony

Meizu had a unique home button called "mBack" that combined touch gestures and physical presses for navigation. A light tap would go back, and a full press would go home.
#Meizu

"Light-up notifications"
RGB LED back on Alcatel A5 LED
#Alcatel

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