You can no longer carry them on planes, but you should have one in your right front pocket at all other times.
A small, Japanese-made (2" closed) Higo knife, with brass handle and soft-iron blade. Hand-made (Japan) and hand-finished at our shop here in Dallas; no two will look the same.
The soft steel produces a very sharp edge, easily honed as necessary. If you live in more humid areas or use it on fruit, a drop of oil every once in a while won't hurt.
If you need a larger Higo, look for Townes, Cash or Blue elsewhere on our shop.
Consider adding a knife care-kit, which includes a small sharpener and oil (shown with Townes). Details under Knife Care-Kit.