An extra pair of gloves. I thought I was ok with my fancy new waterproof gauntlets on my last trip, but I wish I had packed this:
One set heavy waterproof touring gloves, and a pair of light, fabric motocross gloves. Especially when riding in and out of rain and mountains. You might actually prefer the lighter gloves in the rain, since they're less sticky and will dry quicker. It's nice to have the option.