For me its the ‘Knock Code’ that LG had on their phones (I really wish LG still made at least the V series phones)
Basically there was a four-square area and you set up a sequence of where you would tap to unlock the phone. That set of squares was only shown when you set up the code
Then, to unlock your phone, you would tap those areas in the sequence you set up (even with the screen off).
Fingerprint readers are nice, but I really do miss the knock code
Edit: did find this article with a way to do the knock code, but if done wrong, could brick your phone I guess.
Plus, article is from 2014. When I looked at XDA’s info on it (they also being the developers) it looks like development on it is over, but individual modules may or may not still be supported by their devs
Aux ports are nice for versatility, even if I was already using wireless earphones. Along with being able to listen to FM right on your phone. It’s features I don’t use often, but occasionally. I wish the USB-C connector had the option with a clip. IR-blasters were useful and much fun. I never even used the actual remote to manage my LED strip.
I never realized notification lights just kind of stopped existing. But I don’t miss them in light of always on displays. Under screen finger print readers is basically a dream come true. Having multiple cameras is nice. OLED screen is an absolute godsend. Overall I’m not unhappy.