I don’t really give too much thought to mundane items. They are just the essentials that sit on your character sheet, barely noticed or acknowledged except on rare occasion. About the only common exception is rope. Every character I have ever created must have rope. Usually 100′ of silk rope if I can carry it without being encumbered. Rope is absolutely essential to survival in every single campaign I have ever ventured on.
Other items come in handy from time to time, but not regularly. Tinder twigs, chalk, marbles, caltrops, crowbar, alchemist’s fire, and so on. Aside from rations, though, only rope is absolutely critical.