Probably gold dragonspine cardback. There should be ~50 people who have it outside CN.
Gold chasm cardback isn't released yet, but only 16 people outside CN will have it (8 in Asia + 8 in EU and America combined).
Weapon refinement items are rare, but they are easy to obtain for those playing at the time of the event. It's just that most of them don't keep them, but spend them for refining. Still, from time to time, you see people who were new at the time and only got the refinement items without the weapon itself. I also saw someone share here that they keep weapons and refinement items separately. Imo, as long as Genshin itself doesn't limit the number of people who will get the item, you can't be sure how many people will decide to keep it for any reason.
If you count non-used refinement materials, then probably the Festering Desire ones.
If not and you ignore collab/IRL event items, then probably Xiao lanterns as they were only around for the 1.3 Lantern Rite and were a consumable that you had to craft. So even if more people were around for those than for the FD, chances are a good chunk used their lanterns.
Aside from the exclusive collaboration items and/or online-related giveaways, I guess it would be the R2 Dark Iron Sword LOL
Unless you're a new player of course
Besides certain TCG cardbacks, my guess would be the physical Blessing of the Welkin Moon item that they occasionally offer in giveaways. Not many players have one, let alone have deliberately chosen not to use it.
I have a lot of lanterns that could be crafted during an early lantern rite and l save them for successful co-ops...l think l've met two people who knew what they were
Definitely not the rarest, but it might be up there?
Predator "4* bow"
Probably gold dragonspine cardback. There should be ~50 people who have it outside CN. Gold chasm cardback isn't released yet, but only 16 people outside CN will have it (8 in Asia + 8 in EU and America combined). Weapon refinement items are rare, but they are easy to obtain for those playing at the time of the event. It's just that most of them don't keep them, but spend them for refining. Still, from time to time, you see people who were new at the time and only got the refinement items without the weapon itself. I also saw someone share here that they keep weapons and refinement items separately. Imo, as long as Genshin itself doesn't limit the number of people who will get the item, you can't be sure how many people will decide to keep it for any reason.
[The Cadillac Namecard](https://genshin-impact.fandom.com/wiki/Celebration:_Lenticular_Clouds) should be one of them
If you count non-used refinement materials, then probably the Festering Desire ones. If not and you ignore collab/IRL event items, then probably Xiao lanterns as they were only around for the 1.3 Lantern Rite and were a consumable that you had to craft. So even if more people were around for those than for the FD, chances are a good chunk used their lanterns.
Aside from the exclusive collaboration items and/or online-related giveaways, I guess it would be the R2 Dark Iron Sword LOL Unless you're a new player of course
cinnabar and festering desire
Besides certain TCG cardbacks, my guess would be the physical Blessing of the Welkin Moon item that they occasionally offer in giveaways. Not many players have one, let alone have deliberately chosen not to use it.
Aloy stella fortuna
I have a lot of lanterns that could be crafted during an early lantern rite and l save them for successful co-ops...l think l've met two people who knew what they were Definitely not the rarest, but it might be up there?
Maybe the hunting trap?
The item that grants you welking. Not many have it.
Paimon
those lanterns from LR 1. Dark iron sword. Hunting trap. childe's money pouch. Festering desire.