Looking through all these posts makes me wanna buy a bunch of mice, too. But only one expensive hobby at a time.
Anyway, these days I'm using the Logitech M570 trackball mouse. It's a strange adjustment to regular mice to a trackball one, but I like the convenience of no longer having to move my hand in my considerably small amount of keyboard trays. It's very comfortable and great with the TKL keyboards I have. I would have considered the other trackball mice, but this was on sale on amazon.