also: めずらしもん
noun
rare item; unusual thing
Refers to something that is not commonly seen or found; can be used for objects, occurrences, or people with a unique quality.
この店には珍しものがたくさんある。
This shop has many rare items.
彼はいつも珍しものを集めている。
He is always collecting unusual things.
珍しい is the adjective meaning 'rare' or 'unusual', while 珍しもの is the noun form referring to the rare item itself.
Compound of 珍し (めずらし, stem of adjective 珍しい 'rare') + 物 (もの, 'thing'). The colloquial variant めずらしもん reflects a common sound change where もの becomes もん in casual speech.