This thread is full of good suggestions so here are a few that might not have been mentioned:

• Torrent Control - useful for sending magnet links directly to a variety of clients.
• Offline QR Code Generator - good for quickly sending all sorts of stuff to a phone or tablet.
• Better YouTube Shorts - depends if you like them, but this adds autoplay which I love
• TamperMonkey - extensions for your extensions! Usually site specific.