I have an old Logitech M505 mouse and I really like both the ergonomic form factor and the fact that it's from Logitech (the Unifying Receiver is handy). I looks like this:
But this is discontinued and it has a few problems of its own, so I'd like to find a new similar mouse from Logitech.
But it must have a clicking scroll wheel (so rotating the scroll wheel clicks into set steps instead of smoothly scrolling). Also the scroll wheel needs to be the middle mouse button (as opposed to having a separate button below that acts as the middle mouse button). It should also have a similar form factor (meaning no weird gaming mice that look like they're an Autobot or Decepticon). Other features (like additional buttons) are okay but not required.