My favourite less known app: https://www.inyourface.app/ - This amazing app throws up a fullscreen modal dialog with a countdown to your next calendar meeting and has a button to click to open the Google Meet, etc. I set mine to countdown 1 minute before it starts. I'm almost always on-time for meetings now. It's also included in SetApp.

SetApp - Mentioning now because I mention below ones included in SetApp, it's a monthly all-you-can-eat subscription to a few hundred mac apps. It's an alternative to purchasing them separately. It may well work out cheaper in the long run to just buy them but it's a useful option.

Adjust third-party Monitor Brightness - Lunar.app for a standalone tool with the most features (can automate and sync the brightness adjustments with time of day, your laptop monitor, etc). But basic control with the keyboard buttons is possible also from BetterDisplay. DisplayBuddy is another tool in this space. They have varying features and pricepoints.

BetterDisplay - Enables HiDPI support (e.g. "more space", "more text", etc) on third party displays - makes text size bigger for people that prefer it on 1440p/Ultrawide QHD displays nicer for many and apparently much nicer for 4K displays for most people though I've not used a 4K.

Multitouch - My current favourite of the various tools that both let you snap windows to the left/right half (or third, etc) PLUS let's you assign three finger click on your touchpad to middle click for opening tabs in Chome. There are a bunch of others apps in these spaces but this is my current favourite in terms of the exact features I need, in 1 app, with a good price point. See also BetterTouchTool (also in SetApp), Rectangle)

iTerm2 - Mostly I love Terminal.app, except, when screen sharing in chrome it won't share multiple tabs for some reason, plus, it's the only terminal emulator on any platform that supports tmux integration mode so you can open multiple screens on a remote SSH server that appear as physical tabs or windows locally.

Secretive - Creates SSH keys in the secure enclave that cannot be exfiltrated by Malware, optionally it can either support "No Auth" or require TouchID/Password for each use. I have one of each style, for differing security levels of hosts.

yubikey-agent - Automates using your YubiKey as an SSH agent and makes it work every time you plug/replug.

Karabiner Elements - one of a few different ways to make home/end on third-party keyboards work on macOS.

More commonly known ones: iStat Menus (also in SetApp)