I've enjoyed everyone's wristies over at hammockforums.net. I suffer from hands that get cold, and STAY cold. That's despite being otherwise fairly hot-natured.
I've considered re-purposing old sweaters like others have done (and probably still will). I settled on a fluffy pair of merino wool socks that I picked up cheap and have been sitting around since I wear low-cut socks most of the time.
I cut a short slit for my thumb. Then I decided I could widen it slightly and I also have convertible mitts! I can fold back the "fingers" portion, tuck it under the (backhand-side) wrist flap. In addition the folded over part creates a double layer of fluffy merino for great warmth!
All I have to do for a nearly enclosed mitten is twist slightly & the nearly sealed thumb hole is in my palm.
Add my SUL ultra hi-tech WP overmitts (bread bags) or my OR WP mitts & I can stay warm in very cold & wet conditions.