Firefox because it's plugins make mobile browsing bareable. I have a folding phone so I wish that Firefox would hurry up and copy Chrome's multi window feature, and then it would be the perfect browser for me.
I use Firefox on desktop too, but I've been experimenting with Arc the last few weeks to see what the fuss is about.
I used to use this one...but for some reason I just never found any of the settings made it as noticeable and useful as an actual notification LED so I just switched to using an always on display.
https://play.google.com/store/apps/details?id=com.jamworks.aodnotificationledlight
I too miss notification LEDs...yet another thing sacrificed to the alter of bezelless design.