I ordered the PicoPen. Nobody mentioned it in this thread, but searches for other pens brought it up. From reviews, the PicoPen is uncomfortably small and sometimes the magnet cap releases without intent. However, most important to me is that it's small. The PicoPen should fit my need for a pen to take quick notes if no other pen is around.

I also ordered some Rite-in-the-Rain notepads.