I've carried all types of pens and pencils over the years.

As far as pens go, for the last year or so I've carried a Pilot Dr. Grip Gel or a G-2.

They write well on all sorts of different materials. Sometimes you have to give'em a few seconds to let the ink dry.
Plus they both use the same refill.

I usually carry a Pentel Quicker Clicker mechanical pencil in .9mm. I have a pretty heavy hand when it comes to pencils, and most of the smaller lead diameters seem to break to easily.

And last but not least; a black Sharpie. Nuff said.

porkchop