Geostuff Carabiner Pen
Here is a handy pen that you can clip onto a lanyard, belt hook, shirt buttonhole....
How infuriating is it to have trekked into a cache, or climbed a steep hill only to discover that you don't have anything to sign the log! With this clipped on somewhere you will always have one handy. Also has a retractable ballpoint so you don't accidentally draw over yourself!