Weapon of choice

Robin, you are on a roll ;-)

In the iMac I use a tiny Microsoft mouse (I like its wheel better than the one from Logitec (to loud)). On the laptop I love the trackpad. It can be very precise and the hand are much closer to the keyboard.

Logitech Performance MX mouse: Works for me.

I’ve been using a Wacom tablet and stylus since 1990, specifically to pre-empt carpal issues, which were a big thing (newsworthy) back then; have managed to stave off debilitation, except for a small callous on the end joint of the little finger.

I switched from a Logitech MX mouse to a Wacom Intous Pro Pen and Tablet about five months ago because I was experiencing recurrent wrist and shoulder pain. Prior to the switch I made all kinds of adjustments to make my mouse use more ergonomic to no avail. Switching to the pen and tablet has been a game changer for me, even though it took some time to get accustomed to the change.

Logitech M705 mouse and slanted mouse pad, and a Microsoft Natural 4000 Keyboard. The keyboard is fairly ugly, the keys are loud (the spacebar is even louder) and they wear out quickly (~1 year), but I have not found anything close to being as well designed ergonomically. Most mice with programmable buttons are too big, the M705 is nearly perfect.

I’ve been a Kensington trackball user for over twenty years. It’s easy on the hand, if I’m not moving the ball it just stays put, and it saves desktop real estate because it doesn’t move. I’ve tried dozens of other peripherals over the years and none of them made me as happy. The only drawback is that they stopped making them in all white, which looked great when the ball was swapped for a billiard ball.

If I did have to go back to a mouse it would be the Microsoft Intellimouse Explorer. Microsoft’s designers absolutely nailed that design, which is why it’s still selling after 18 years. Sometimes I miss the days of Windows 2000, an Intellimouse, and a Trinitron CRT running at 1600x1200. But I don’t miss the modems!

Add me to the list of those using a Kensington trackball. It doesn't need a lot of room and I rest my hand on it rather than clutch it. With two screens, it makes it easy to fly between them with just a brush of the trackball.

I also switch sides every few months to prevent overuse of one hand.

I also can't use any other device but the simplest, most standard, compact and light plastic mouse. my current one doesn't even have a brand on it. I handle it with the tips of my fingers with minimum effort. 
Years ago I suffered a lot of wrist and finger pains from mice I had to fight with for long hours, I moved from it to Wacom tablet and pen for several years (as a total replacement for a mouse, not just for creative work), it also operates with no efforts so never caused me pain and fatigue, even though the pen buttons were always a bit tricky to operate. I used to set the tablet's "active area" to about 9x7cm (something at the size of a track pad or even smaller) which enabled very quick and easy cover of the screen with reasonable accuracy. 
It may have been that I lost the tablet's pen or gave it to someone one day, I'm with the most humble mouse out there since.

If you want to keep your favourite mouse going forever, switches are usually standard sized parts and easily replaced. Some Logitechs have a weird switch but you can find those on eBay. Sometimes, I steal a switch from one of the many functions I never use. Often they hide the screws under the pads so you should keep spares before opening. For replacement pads, check eBay for "Teflon skates". I trace and cut my own. It's like a new mouse each time.