My current PSK, based on the smaller tobacco tin, features a small Douk-Douk, a Swisstech Utilikey, and a BCB deluxe wire saw with the split rings removed as the main tools. I figure I can use the Utilikey and my Inova microlight as handles for the saw if necessary.

The Douk-Douk is the small one with the 2 1/2 inch blade. Folded it takes barely more space than a stick of gum. Yery sharp, the blade is made from carbon steel. There's no lock, but the slip-joint spring is very strong and the joint end of the blade is squared, so there's little risk of the blade closing on your hands. And you can bend the wall of the handle if you really need a lock.

$15 + ship from Szabo Inc.