...I feel like a member of an increasingly marginalized group these days, but I love my Logitech Trackman Marble.
It's because I've been using Logitech Trackballs for maybe 20 years now, starting with a Marble FX and then later switching over to the Trackman Marble when they no longer made the Marble FX. At some point, I just bought five of it, in case one breaks and they stop making that one too, but none ever did break.
I just like the precision-feeling that a trackball gives me that a mouse doesn't.
Scroll bars have been getting smaller and smaller over the years and over these last couple of years I've started to really get into trouble with more and more UIs deciding to turn them off completely. Of course the people who decide to turn off scroll bars also don't give a hoot about the keyboard, which really infuriates me, when it leaves me with no option at all to scroll.
At some point I added a ShuttleXPress Jog wheel to my "rig" on the left-hand side of my keyboard and I'm having its driver simulate a scroll wheel. But I use it extremely infrequently. (...so I was totally lying when I said I had no way at all to scroll).