Android

Easily notification light. People always say "oh, it's totally obsolete with always on displays". But with a notification light I could focus on other stuff and the blinking light got my attention better. With the AOD, I always catch myself glancing at my phone. Also, the light's color clearly indicated which app caused the notification. I had White for calls, Green for Whatsapp, Yellow for the ebay app, Red for GMail and so on. "You can do all that with an OLED screen! It only lights up the pixels that-" Can you, though? All apps that I tried were utter garbage. Buggy performance, very battery hungry and very cumbersome to configure. I don't know if custom firmwares actually have that feature in a usable state nowadays, as I cannot root my phone anymore without losing core functionalities like online banking.

Yeah, everything tends to go to shit with time. I miss my Galaxy S2.

Apparently nearly everything I look for in a phone. Others have said IR blaster, side squeeze, notification light, and pop-up front camera, all of which were amazing.

I'd add an unlocked bootloader (I bought it, it's my phone to do what I want with), removable battery (hello instant charging), and a small form factor (so sick of needing two hands to do anything).

Not so much a gimmick, as much as something that seemingly went extinct that I miss: rear fingerprint sensors. I loved them on my Nexus/Pixels, and the in-screen one on my 6a is way less consistent and convenient.

Also it flashbangs me when I try to unlock my phone at night.

Front facing stereo speakers were nice.

To show how old I am, a phone without a physical keyboard.

Does IR sensor count? I loved that on older phones so much.

Idk if this is a gimmick but I love swiping on the rear fingerprint scanner to pull up/down the notifications and quick settings. I also got an app that lets me swipe left/right on the sensor to adjust the brightness.

It's been gone for a while now, but I really liked the IR blaster to use as a secondary remote when you can't find the remote because your toddler was playing with it. Dammit Susie!

That pop up camera on the OnePlus 7 pro.

That thing was cool as fuck. My roommate got the phone and I was VERY jealous even though I had a OnePlus 8T at the time.

On my motorola: quick shake side to side to enable flashlight. So easy to use, it's become second nature. I'll have to find a way to replicate that on the next phone I get.

the IR Blaster, absolutely loved it and still do

Material You. I wondered why they wasted resources for ... colors. But it's so nice to have a consistently colored UI across apps and across dark/light modes, and I wished that more apps would support it. Also, those pastel colors are less stressful for the eyes than the previous grey/blue.

I know it's not everyone's taste but I really like it.

IR blasters. They were nice as a little pocket universal remote.

The air gestures that Samsung put in the S5. It was a gimmick, but a useful one, since you could use it to control things without having to fiddle with the screen.

Also the screen-off gestures on the Oneplus 5. It was great for turning the torch on or opening apps without having to faff about as much with the screen.

Can't say I love the feature but the front facing camera getting "integrated" into the screen isn't nearly as annoying as I thought it would be.

Power button fingerprint sensors. I had one on my S10e, and I loved it - with the way I held the phone, my thumb naturally rested on the power button, so it was pretty much auto-unlocked.

Now they seem to have fallen by the wayside in favor of in-screen sensors - which are cool, but ever-so-slightly more cumbersome. Ah well, still better than facial recognition.

Nokia N95 flipping both up and down. I really liked those music player buttons when flipping it down

Workspaces in Linux window managers. I thought it was a dumb idea at first but I tried it and found workspaces are great.

Tablet computers. My thoughts on the first iPad were that it does everything a laptop, an iPod, and a Kindle all do, but worse. Next thing I knew, they were everywhere. I think traditional laptops are making something of a comeback, though.

My wife has an iPad and after using it for a bit, yeah I get it.

Allo was the best messenger. So many useful features

Removable battery, micro SD, sim slot etc

On pixel phones, the squeeze for Google assistant feature. I used it all the time on my old pixel 2xl.

Folding phones.

I was so skeptical at first, and even now it seems most people still are. It's a complete game changer though. There's almost nothing I can't do on my phone anymore, due to the multitasking and the larger screen. I can comfortably use desktop websites when necessary for banking etc. I have watched many dozens of movies and tv shows on it. It's just nicer for reading and browsing the web, and makes your phone feel so much more powerful to have the tablet form factor. I've actually been travelling for over a month with no laptop, just my Fold and a Steam deck.

I'm also appreciating having what is essentially a 5G-connected tablet where in the past I've always dismissed the LTE-connected ipads as a gimmick. It's hard to justify paying extra for the device and then a monthly fee, but now that I have it I can definitely see the appeal of a tablet that just works anywhere you go. Except since it folds you can put it in your pocket too.

FM radio. Also my old Motorola had a "karate-chop to activate camera" which was very useful

The active edge squeeze feature on the pixel 3. I loved being able to gently squeeze the sides of the phone to trigger google assistant.

Probably the Quick View Window case on the LG G-series phones. The overview on notifications was great and allowed answering calls without opening the flap while protecting most of the screen. Also the reduced visible screen space did not blast you with light when checking time in the middle of the night.

Fingerprint sensors

Retractable fountain pens. I could never afford one though.

Keyboards, optical scroll, and IR blasters.

Idk if this counts as i dont really involve myself in a lot of discussion, but MAN do i miss two button navigation. it may still be present in some other Android distros but on Graphene an update removed it for me a while ago.

IR blaster, removable battery, MicroSD slot, analog headphone jack, unlocked bootloader, stylus. The Note 3 was the peak of android phone design. I'm using an S22 Ultra nowadays because of all those features I'm a huge slut for the S-Pen, even to the point of sacrificing all of the others... But I'd love for the rest of those to make a comeback.