[ahelwer]

Mice, as in things you drag across a desk surface, are a complete dead end ergonomically. Trackballs are the answer. I like the Kensington vertical trackball. The only thing that moves is your thumb. Those small precise wrist movements kill you.

[coryrc]

I moved to a trackball, a large one. Made my wrist hurt after a ~week, so I went back to a regular mouse (which has never caused me pain) or, my favorite, using the trackpoint (but unless I want to shell out crazy money and wait a while can't get a split keyboard version, so it's only when using the machine away from my desk).

[yellowapple]

Seconded. I'm partial to Logitech's MX Ergo; I feel like fully vertical is a bit of an overcorrection, whereas the Ergo lets my hand rest diagonally, which feels a fair bit more natural and comfortable. Bought one on a whim for work, and I've enjoyed it enough that I bought a second one when I switched jobs this year.

[perlpimp]

tbh magic mouse pad with three finger drag has transformed my interaction with computer and Cooler Master master keys M(that they don't make anymore) given me numpad and cursor keys and navigation/edit keys very close. It is like 1/2 more ergonomic this way.