When I did my signals course in the British Army we were always told to use a pencil to transcribe radio messages. The reason is because it is quicker to write with a pencil and they are always more reliable than a pen.

The only other writing implement needed is a permanent lumocolor pen for writing on laminated maps. We used to use chronograph pencils but lumocolor replaced them because they are not so messy. To remove permanent marker from a laminated map use cigarette ash.

The pencil I have used for the last 22 years is the Staedtler Mars 780 2mm lead holder. These are very reliable, It does not matter if the lead breaks into mutable bits, do not need sharpening although there is a sharpener in the end and are very reliable. I have two that are both working fine after more that 20 years. And I fined the leads last longer than a standard pencil.
http://www.cultpens.com/acatalog/Staedtler_Mars_780_Leadholder.html