My main workflow mouse has been the Logitech g600 for years. I love having 24 different macro keys accessible with my thumb (stuff like copy/paste, ctrl+w, ctrl+shift+t, enter, etc), but it's terribly un-ergonomic and the software is terrible (and doesn't let you configure settings except through its eye-watering UI). And afaict, Logitech actually stopped making them, so I have to snap them up whenever resellers put one on Amazon, since the main mouse button switch has a nasty habit of starting to double click after too long.

It's to the point where I'm considering just commissioning a hardware hacker to make me a custom mouse.

I love my G600 as well.

I think I nearly know how to replace most of the mouse.

I can resolder new switches, mouse-wheel button and those buttons below the mouse wheel.

And replacement pads for the mouse feet are easy to buy, if not, you can buy a pad uncut and custom-cut it.

I just now need to learn how to replace the side dome buttons individually instead of replacing the whole PCB, since I cannot keep buying replacement mouses for just those side mouse buttons as the price seems to be creeping up with the increasing scarcity.

I was hoping for so long that Logitech would make a wireless version of the G600, but instead they killed it. I'm begrudgingly using a wireless Razer Naga now. It's pretty crappy though because it doesn't have onboard profile storage so you need to run their bloated software just to remap the buttons. Also it lacks the awesome ring finger button that the G600 has, despite the Naga having space on top that could have been used for an extra button.

My favorite, and I have spares, but I will be heartbroken when I work through them....

Would really be glad to know of a contemporary equivalent with USB-C.

I highly recommend swapping switches, it's a noticeable upgrade