Rite in the Rain's All Weather Pen writes in any weather, virtually any temperature and upside down.
Rite in the Rain says:
Black Ink Tactical All-Weather Clicker Pen. Pencils work well on Rite-in-the-Rain waterproof notepads, but for more clearly-defined writing or drawing sometimes you just need a decent pen . This 5 1/4 inch long metal all-weather pen writes on wet paper and even upside down, and will operate effectively in temperatures ranging from -30F up to 250F.
Rite in the Rain's All-weather Pen is the perfect companion to Rite in the Rain notebooks and other products. Its made by 'Fisher' who became famous for the Space pen - they produced a pen for NASA that would work in zero gravity (most pens require Earth gravity for the ink to flow out of the nib) by pressurising the cartridge - this is how the All-Weather Pen manages to write upside down.
More usefully it writes over water, grease and onto photographs - a wide variety of contaminated surfaces that would challenge other pens!
