Ran into a fellow geocacher while on vacation and noticed he carries gloves with him. It seemed like overkill at the time, but a few days later I found a cache that was soaking wet and smelled like poo . I couldn't get the smell off of my hands for the rest of the day.
Now I bring gloves: plastic disposable ones for potentially icky situations and cheap leather ones for digging around in dirty spots. I suppose they might qualify as a good addition to the first aid kit I keep telling myself to buy, too.
