What I used:
Yarn: Mission Falls 136 Merino Superwash - Tri-color Granite (any DK weight yarn will work), This is my first project with this yarn and I like it a lot. Warm and soft.
Straight needles: Size 7 and Size 8
The pattern for these hand-warmers is basically this one (lots of other cool stuff here too), except I left out the eyelets and started with a slightly larger needle. Also, I used a twisted rib, knitting into the back of each K. The pattern worked brilliantly for my hands, with no alteration necessary.