Gerber 200 (USA). This one fits on your key-chain, stays sharp. Hasn't been made in 20 years so set your eBay search for it. Goes for $15-25. Take it off your keys before going on a plane.
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I bought a dozen of those in various sizes many years ago.
The greatest lil knives ever, but only have 2 or 3 remaining - they are so small and lightweight they vanish easily.
I used to work at a large bureaucracy, in a 30's 'nazi-deco' (my girlfriend coined that term) style building with beautiful handcrafted wood and brass doors - and locks - where they required you to physically sign up (on paper!) for access and a key (on a huge fob) to each conference room for meetings. (Ok, the building
was open to the public).
I enjoyed using these knives to pick those old locks so I could have meetings on-the-fly
without jumping through hoops with some drone in an office 7 floors up!. The knives were so small I could just 'lean up' against the door, looking around casually while I slid the latch open.
The 'bosses' never caught on, nor to the fact that, when I
did sign out a room, I always 'signed' as one of the constitution signers, or Abraham Lincoln.
Wonder why I never won any great promotions there....
Still use two of the surviving knives on a near daily basis!!