+ 4 or 5 or whatever on the Fisher space pen. My problem with pens in the truck (in the middle of Texas) was not drying out. It was popping and the ink leaking everywhere. I even had a sharpie pop, so I wouldn't go that route. Then someone gave me a Fisher bullet pen for Christmas. I thought it was ugly and stuck it in my truck. Made a believer out of me. Still one ugly pen, but very reliable and tough.

REI has a version that looks really nice. They have the Stowaway by Fisher for $8.00, and the Inka for 19.95.
http://www.rei.com/search?vcat=REI_SEARCH&query=pen&x=0&y=0