weirdly, the best mouse I've used is perixx mx-2000

the newer years aren't as good as my older one (now like a decade old if not more), but they're still more comfortable than any other mice I've tried. which I find weird because it's all sharp edges and stuff. but it just works for me. and I do have RSI issues

I also find it's the mouse where I had to reposition my hand the least. I'm currently using some razer mouse I think, and I've tried a bunch of other ones, and all of them have smooth surfaces where I find I lose my grip and it's like anti ergonomic because of it. whereas the perixx had a nice sharp edge that I could very lightly hold on to