The Victorinox Scribe Swiss Army knife is the smallest pocket knife model that includes a retractable pen. It is extremely compact and convenient (the Scribe weighs 17.4 grams, or about 5/8 of an ounce).

NOTE-- This model has also been called the Vintage II Swiss Army knife. Its Victorinox model number is 0.6126, or #54881 in the US.

Classic SD-- no pen, adds scissors and toothpick
Escort-- no pen, adds toothpick
Manager-- adds scissors and a bottle opener/combination tool
Signature-- adds scissors
Stylus-- no pen, adds a retractable stylus