What I've been doing: instead of getting into crazy wrist rests, pads, or insane "ergonomic" products that feature an asinine design, I've been focusing on positioning of what I use.
At my desk (at home), I made a KB/M tray that slides out.
Based on where my computer chair is at, my eyes stare out to about the middle of the top third of my monitors. My arms/wrists mostly fall naturally to my KB&M. The arm rests are dropped/raised to the point that basically sitting relaxed will naturally have my elbows find the supports, but only when I want that.
If I drop my elbows/forearms to rest, the angle betweeen forearm/upperarm is a, I dunno, 100º ? It's a little more open than 90º.
When I'm gaming, I adjust my chair so I have a good sitting position and gives my elbows a chance to stay on the rests and keep fairly close to that when actively engaging the KB&M. If I get this all setup right (hard to really describe exactly what I strive for without writing up a lengthy article), I don't feel any soreness/fatigue in any part of my arms.
If you regularly feel fatigue, that's a sign you're stressing things you shouldn't.
For reference, I use a Logitech G700. I'm right-handed, btw. The way I hold it, my palm/wrist is in a naturally "open" grip, and only a little bit of the outside of my wrist makes contact with the surface. If you hold your right hand out, palm facing down, the "right side" of the bottom-facing portion of your wrist is the only part that should ever make contact with surface. If you have the entire portion of the wrist making contact, in time, you will most likely develop some shade of CTS, as that is how you create the pressure on the nerves that leads this the problem. Essentially, the wrists should be "slightly tilted" in that the outer portions are at the lowest and the inner part is elevated.
For me, it helps to combine that style of mouse use with good ergonomics of arm and back positions, to make it natural and reactive (for gaming).
