The 9th Amendment of the U.S. Constitution:
"The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people."
I always liked this one because it has a sort of mathematical "closure" property. It's not enough to say "this is the set of laws", it's more than that. You can't enumerate all of a person's rights, in effect.say
Legal scholars might argue that this amendment is practically useless, and use the 14th instead. Also the 10th amendment has basically given those rights to the States through precedent.
But I like the 9th. It has Mathematical Beauty, and shows that some laws are unknowable