Custom screen-off gestures
#Bluboo

Draw to search emoji
#Google

Linux on Dex
This allowed you to run linux applications inside desktop mode.
#Samsung

Two fingerprint sensors
#Huawei

Xenon flash
It was available in Samsung S4 Zoom and K Zoom and it was in testing phase of Xperia Z1 prototype
#Samsung

Gesture to Rotate Screen
#Smartisan

Swipe to Clear Icon Badges
#Smartisan

Fullscreen album cover on lock screen
#Google

Samsung Pay MST
#Samsung

Wikitude
This app allowed you to see places from your camera app.
#Sony

Baby crying detector
Once it detects baby crying it will automatically alert you on Galaxy Gear smart watch
#Samsung

Voice Recorder meeting mode
distinguishes sounds coming from up to 8 directions when recording, and indicates which sound comes from which direction when the recorded file is played back.
In particular, when you wish to, you can play back only the voices coming from certain directions by selecting them.
#Samsung

Caller information display feature
When you receive call from someone, sometimes you want to know what the person has been up to lately or about what and when the conversation was made between you and the person. With the Galaxy Note 4, you can check information about the relevant information about the person when you are receiving a call from, or making a call to, or even during a call.
#Samsung

Tilt for a Customized Playlist
Tilt the Galaxy S5 horizontally (into landscape) while listening to a song via music player, and your Galaxy S5 instantly suggests similar tracks among the songs stored on your phone based on information of the current song, such as its genre, mood, source, etc. So the more songs you have, better the recommendation
#Samsung

Virtual Tour
feature that allows you to take pictures as if you are giving a tour of the surrounding area to viewers.
#Samsung

Merged functionality of 2 button navigation with 3 button navigation (Only available in android 9 OneUI)
#Samsung

Built-in 360° camera
#Protruly