I don't think items can be really "rare" at this point. People are willing to time travel for items only available on specific holidays. People are also willing to dupe one-time DLCs.
I obtained several Berliners actually and I don't own a German game nor DS. I also obtained the grapes, tweeter and juice without visiting other towns.
To define what's rare you'll have to give a definition of what you feel is rare. Items that can only be obtained on a certain day shouldn't be considered rare since time travelling will enable you to obtain as many as you'd like. What I would define as rare are unorderable items from foreign games, specifically Japanese and Korean, since not that many players in the Western world (or this community) own them. For example the Korean new year item Bell Knicknack or the somewhat easier to obtain Japanese New Year Noodles.
The Zodiac set shouldn't be considered rare since they can be obtained in all games. The horoscope set shouldn't be considered rare since it's orderable. One might even say the special items sold only on Club Tortimer islands are rare, since they can't be ordered, time travelling is no guarantee that you will obtain one, and you can't invite others to visit the island.
I'll add in the cardboard/sloppy stuff since it's pretty hard to obtain. I think it's even harder than island stuff. I've only ever ran across 1 sloppy item in my Re-tail and there's no method to make them appear either. :/
I'll add in the cardboard/sloppy stuff since it's pretty hard to obtain. I think it's even harder than island stuff. I've only ever ran across 1 sloppy item in my Re-tail and there's no method to make them appear either. :/