I found a Thacher Cylindrical Slide Rule [1] in the garbage once at the university I worked at. I didn't have a holy grail list for such things, but it assumed that role when I found it.

[1] https://americanhistory.si.edu/collections/object/nmah_11312...

The Curta is the ultimate calculator to own. I wish someone was still making modern replicas, but it seems that it's just too complex or at least too complex to bother with. So we're stuck with scavenging the ones that are still working off of individuals. I hope to buy one someday if there's still any supply of them left on the used market.