I’m not thinking of a material like paper but an object with a design so perfect that it has not been changed in a long while. The only thing I can think of is a bobby pin.
The wheel?
Sewing needles, spoons, bowls.
Needles are a lot older than booby pins.
Combs are a lot older than bobby pins, but I think the winner is going to be something like a bowl or spoon, maybe a hammer.
The knife? a sharpened piece of metal for cutting.
Paintbrush? animal hair attached to a stick for painting on cave walls/papyrus.
Fountain quill pen?
Aren’t we going to get bogged down in definitions here? People still use arrows and spears, but a modern carbon fibre competition arrow is arguably an entirely different beast from a stick with a sharpened stone hunting tip. The same goes for the wheel - roughly circular piece of wood on an axle, or alloy unit with low profile tyres and bling bling spinning outer rims?
an Axe.
I think you’ll find they’re a lot less painful if you use them in your hair.
Haven’t sewing needles changed as manufacturing techniques improved
I don’t know how to reword my question to eliminate spoons and bowls. 
Asking for a list of the top ten (Bottom ten?) items might yealt the results you’re looking for.
I think we should be able to find something that predates the widespread use of metals.
Are you thinking of things that were either patented (or would be patentable had there been appropriate patent laws when they were designed), and that are currently in use in a form substantially like the original?
For example, a paperclip?
I’m not sure why you’d want to - once you start making exceptions and disqualifications, what’s the point in asking the question?
They’re still a thin rod with one eye at one end and the other end very sharp. The oldest ones I’ve seen were stone, not even metal. Larger than the steel ones you get now? Sure. But nobody would take them for anything but a needle.
Knifes and axes were also in use during the Stone Age.
Bricks have been around a long long time. Baskets too.
That was my very first thought. A random object perfected to clob another random object, yes?
Weren’t early knives just sharpened rocks?
Flintknapping is observed in some nonhuman primates and I’d think predates humanity. Sticks for poking insects out of holes are even used by nonmammals like some birds.
>a design so perfect that it has not been changed in a long while
Where do you draw the line on “changed”? Is a simple metal rod today the same as one of ancient Egypt if all our alloys today reflect some tiny amount of 1990’s engineering influence?
Flint tools of various types, specifically designed to accomplish of specific tasks are designed tools, and are arguably many hundreds of thousands of years old. Try making one, one day, with nothing but chunks of flint. It is not a trivial art, but a very carefully learned technology.
Tris
Maybe think about it like this. If you had the original version in your hand, would you use it, or would you automatically reject it for a modern version?
I can’t imagine terribly many people choosing to use an ancient needle or hammer, though many might use the original paperclip.