しい(めずらしい) Unusual.   $$$
まれ Also means unusual, but more formal/newspapery. Also has the connotation of rare-because-it’s-valuable (endangered species, a rare talent, etc.) If you see a dog-turd shaped like Lyle Lovett, that’s 珍しい, not まれ。
(きしょうな) Rare animals or plants. academic word.   NP
(みょうに)  unusual and strange! Usually used about behavior. Something strange is going on, I can feel it! She’s acting strange today. That homeless guy is acting weird.