Pelican 1010 Micro Case
A tiny crushproof waterproof box, and the appeal has not changed: some things need to survive being sat on, dropped, or submerged, and a pocket does not offer that.
What it is genuinely for: the small expensive things that fail when wet or crushed. Spare camera batteries and cards, a hearing aid, medication, a key, a GPS, a phone on a boat. The case is the reason those things still work at the end of a rough day.
Why the hard case rather than a bag: a dry bag stops water and does nothing about pressure. A Pelican-style case with a rubber gasket and a purge valve handles both, and it floats.
What to check: that it is big enough, because everyone buys one size too small; that the gasket is clean, since a hair across the seal is how these leak; and the purge valve, which equalises pressure when you change altitude and is the part people do not know is there.
The trade-off: it is rigid. A hard box wastes space in a packed bag in a way a roll-top does not, and it is heavy for its volume. For clothing and bulk, a dry bag wins; for small fragile items, this does.
Still made, and the small cases are cheap enough to be an easy recommendation. Pelican's lifetime guarantee on the cases is real and worth knowing about.
The habit worth having: keep one in a consistent place in the bag, with the same contents. Most of the value is knowing where the important small things are without searching.
Part of the guide to gadgets and power.