Thought I’d start a thread where GNOME users can mention extensions that they find particularly useful. Sifting through them on the site is a bit of a chore.
I’ll throw a few out there to get started:
Extensions
Creates a menu of your installed extensions, allowing you to enable/disable/configure them from a taskbar icon.
GSConnect
Allows you to connect and do a number of things with your smartphone. My understanding is that it is essentially a GNOME wrapper for KDE’s extension.
Dash to Dock and gTile are the only extensions I download at the moment.
I love Gnome and it is my current DE but the only thing I can’t stand is that you can’t tile your windows to take up a 1/4 of the screen. The only option by default is tiling to half the screen.
gnome-shell-pomodoro. Even though it’s a bit flaky at times, still helps me focus and keep track of my time.
I am on Ubuntu 19.10 Beta at the moment so I’m using their appindicators extension. Otherwise, this is what I use to tame the GNOME.
Dash to Dock
GSConnect
Media Player Indicator
Sound Input & Output Device Chooser
Touchpad Indicator
Ubuntu AppIndicators
User Themes
I don’t use GNOME and havent for a while but when I do, I would always install this one Quick Close in Overview ( I used to maintain it as well )
Activities Configurator, Dash to Dock, Emoji selector,
Dash to Panel and Arc Menu are the primary ones, I usually end up installing Caffeine and a couple others.
I’ve been on Pop!_OS for a while now, and have gotten quite used to the Gnome DE. Here are some go-to extensions I use:
I’m normally a purist, but for whatever reason, the last month I’ve doubled down on them (must be something in the water 
). Here’s my current list:
@bumdeedharma @kj4ohh reminded me of Emoji Selector and Caffine 
I consequently downloaded them immediately to add to my collection.
I also have a few System76-specific ones but that’s due to my using Pop.