Having at least one slip-joint (non-locking) folding knife is a good idea. Lockblade folders are outlawed in many countries (especially in Europe). Having an innocuous looking slip joint will give you better protection than using your fingernails. I prefer to carry the Spyderco UK Penknife when I’m in Europe.
Learn about more non-locking options in the article below.
Slip-Joint Knives Buyer’s Guide