For this, it’s better to use weird, or strange, or odd.

In English, “rare” always has *positive* connotations: “a rare beauty”, “a rare gem”, “a rare book” etc. If something is “rare”, it is often valuable. For negative connotations, we see “weird”, “strange”, “odd”, etc. (Note: “rare” can also refer to meat that is not cooked for very long. This is neither positive nor negative, but depends upon your tastes.)

It's rare to find people who don't like speaking a second language.

"The way she dances is rare." without more context feels a bit weird to me, but it's not strictly incorrect, since "rare" is an adjective that is modifying "the way" in a grammatically valid way. -Context where it could work: "The way she dances is rare in this part of the world; most styles here are more traditional." For some reason "unusual" feels more natural to me, but I think it's just a matter of connotation and style. "He is rare" is fine. I can also imagine it sounding awkward. I would need more context to be sure. -Context where it could work: "Is he a typical sort of person?", "No. He is rare. You don't see many people like him these days" Basically, it's difficult to be sure if it's awkward or not without more context, but it's grammatically sound I think (other than "dances").

It is rare to find fresh strawberries in the winter. (Meaning It’s doesn’t happen very often.)