In this list, we're taking a look at some of the rarest licensed skins in Fortnite. We won't be including the Icon Series or Battle Pass exclusive skins for this.
Star-Lord Outfit (Marvel)
EDIT: This skin has since been released in the shop and is no longer considered as rare as the Black Widow skin below. This is the first "licensed" skin to my recollection; the wording on this skin is very interesting. While most Marvel skins retain the actual name of the character, this is listed as the "Star-Lord Outfit". It's likely we'll see the return of Star Lord at some point like we did Black Widow, although it's unlikely this original variant will return to the shop. It was last seen on May 6th, 2019. It's likely we will see Star Lord return to the Item Shop, similar to how Black Widow was re-released, but this variant may be lost forever. With most all Fortnite Shop skins making a return at some point or another, the licensed skins are likely to be the rarest due to the nature of licensing.
Black Widow Outfit (Marvel)
Released alongside the Star-Lord Outfit, the original Black Widow Outfit skin sported a black outfit and a single baton for a pickaxe. Again, with the release of the updated Black Widow skin, it's unlikely we will see this variant return to the Item Shop. It too hasn't been seen since the original release from April 25-May 6, 2019.
Batman (DC Comics)
The Batman Bundle featured the classic comic book Batman and the Dark Knight Christian Bale variant as well. While these skins aren't as rare as the Star-Lord Outfit and Black Widow Outfit, they haven't been available since July 10, 2020. This will undoubtedly reemerge in the Item Shop at some point in time but don't expect it to come up as frequently as some of the other non-licensed content.
Chief Hopper & Demogorgon (Stranger Things)
Chief Hopper & Demogorgon haven't been in the shop since November 6th, 2019. Quite a long time, but then again, we haven't had a new season of Stranger Things since about then, so it's only fitting that this skin might make a return with the new season approaching on Netflix. Considering it's only been in the Item Shop twice now, you can expect this skin to be rarer than some of the other licensed content that's hung around in the shop for a while.
John Wick & Sofia (John Wick)
I think Sofia might be rarer than John Wick as she was a secondary character in the 3rd movie AND John Wick was released as a standalone earlier, but either way, this set is definitely on the list. We haven't seen these two since October of 2020.
Pyscho Bandit (Borderlands)
Definitely a niche pick and the first video game crossover (with Halo's Master Chief and God of War's Kratos released in late 2020) AND the first cel-shaded skin, Pyscho Bandit has only been in the shop twice and the last time he was seen was over 500 days ago! It's safe to say if you have this skin, it's crazy rare!
Zorii Bliss (Star Wars)
This lesser-known Star Wars character was released alongside the other big Star Wars skins available in Fortnite, so it's likely that this one slipped past many hardcore fans or skin collectors. We haven't seen Zorii Bliss since December of 2019, and I'm not sure when we would see a return as she wasn't a terribly popular character. If you have this one, count yourself lucky to have not only a rare skin in terms of release but one that not a lot of people have.
Kylo Ren (Star Wars)
Obviously more popular than most of the other Star Wars releases, Kylo Ren makes the list due to the fact that so many skins released with the Star Wars cross-over event that it's likely that only a handful of players actually chose to pick up Kylo, with Rey being a much more popular choice.
Finn & Sith Trooper (Star Wars)
Rey definitely won't make this list. She was way too popular and during the Star Wars cross-over event, it seemed like every other player was Rey, running around the map. Finn was a much less sought-after character, and alongside Zorii Bliss, he hasn't been in the shop since the beginning of January 2020. Some of the other skins, like the slightly less rare Sith Trooper, haven't been seen in the shop since May 5th, 2020 but still make the list due to the popularity of Rey and Stormtrooper skin release.
Fortnite x Ghostbusters (Ghostbusters)
Yes, I know these technically aren't the actual Ghostbusters, but I had to include it on the list because they're still licensed. The price point for these skins was much more affordable than the other skins on this list- by half. At 800 v-bucks and several different variations from which to choose, it's likely that there are only a handful of these skins running around. The TRON skins will ultimately be added to this list upon their departure for the same reason.