Whether you use it to open mail, prep food, ward off an attacker, perform impromptu surgery, or cut the red wire to prevent a nuke from detonating, the right pocket-sized utility knife can come in handy. Iain Sinclair’s CardSharp 2 ($5 @ Amazon.com) weighs 13 grams and has a compact, waterproof design that fits into your wallet when the blade is docked (when folded it’s just 2.2-millimeters thick — the same size as your Amex card). Also: 6 Of The Best Fixed-Blade Knives Available When unsheathed, the rustproof, stainless steel blade extends to 65-mm long. And there’s no need to worry about the knife accidentally popping open and slicing your … well, you know … when it’s closed and being stored in your pocket. There’s a safety lock feature that’ll keep the blade covered until you’re ready to use it. Also: What To Look For In A Good Knife Due to how slender the blade is, be smart about how it’s utilized. Trying to do something like saw through a tree would be futile, so safe it only for practical use (like the aforementioned bomb-diffusing example). Color options include Teflon black (pictured) or brushed stainless steel.