My rarest system on the list is a loose
Emerson Arcadia 2001 which is a scarcity of 7.
I have the Not for Resale Atari Video Computer System 4 switch woody display unit with the lighter yellow trim which is probably quite rare but it doesn't have its own entry. Cool thing is I got that one really cheap off ebay in an auction that used a stock photo of the normal 2600.
I have the GCE model of Vectrex not the less common Milton Bradley one so it didn't count. I also only have US systems so the foreign rarities don't apply. i.e. my Supervision is from here, not Italy and my Neo Geo Pocket Color is also from here instead of Japan where the black and white version is the more common model.
My rarest game is
Gunfighter / Moonship Battle for RCA Studio II CIB which is a scarcity of 8 just loose.
Also repros are rare because only select few people know how make them. And only small quantities of certain ones will exist if not many people order them now while somebody still knows how to do it or cares about doing it. I'd say they are along the same lines as pirates and clones. My four are all NES - Super Mario Bros. 2j, Final Fantasy IIj, Final Fantasy IIIj and Galaxian. That also makes me wonder just how many Yobo FC Twin systems have been manufactured and sold before they upgraded to better compatibility.