Wooden/metal/plastic wrist rests look cool, but I would never consider them, because they seem more harmful than ergonomic to me.
Based on what I've read about CTS (and also from my personal experience), I think wrist rest should be soft (not too soft though) and work fine even with sweaty hands (cloth/leather/rubberized surface).
I use a cheap no-name gel wrist rest, but I'm considering a Grifiti fat one. I've tried at least four different kinds of wrist rests, but most didn't work for me at all.