Fisher Space Pen because it doesn't rely on gravity to make it work, thus enabling it to write underwater or upside down.
Fisher Space Pen Bullet Pen
Fisher Space Pen - Matte Black – Yoseka Stationery
Fisher Space Pen from a NASA school field trip 20 years ago
Fisher Space Pen Classic The New York Public Library Shop
Shop fisher space pen for Sale on Shopee Philippines
NYPL Vintage Stamp Brass Space Pen
Field Notes Space Pen - Waterproof, Anti-Gravity
New York Public Library Chrome Fisher Space Pen
FIELD NOTES Space Pen Ballpoint (Final Frontier) – WRITER