Skins were introduced to CSGO in August of 2013, and even though it's the biggest market right now on Steam - it wasn't the first. It was actually Team Fortress 2 that was the first game to utilize skins.
Looking back to the first items released to CSGO, it's weird to see how much they have appreciated in value. The first collection ever released was the CSGO Weapon Case with both its weapon skins and knife finishes. The case costs a whopping $37, and the cheapest skin from the collection costs a minimum of $7 currently!
Now that's insane and all, that a case that used to cost about 5 cents once upon a time has gone up this much, but this says nothing about rarity yet. To get to that point, we need to look at some of the more unique skins.
Certain skins are rare because of a bunch of different reasons. And some skins aren't even worth more, even if they're rare, simply because of the fact that they're undesired. Rare and desirable skins are the ones you want to be looking for, and that will filter out a lot of possible candidates for this list.
The database provided by CSGOFloat will be used as a source for this post, and that might not pick up every single private or public inventory, but it should be fairly accurate.
Starting off strong, we can take a skin that anyone would want to have in their collection. The AK47 | Case Hardened, with the "scar" pattern, makes for one of the most unique rare skins on this list. The thing that makes it unique is how good it looks with the insane amount of blue on the finish - more than they usually get. With enough blue, and especially with the "scar" pattern, these skins are called "blue gems."
Whenever you unbox or trade-up for a weapon, you can get 1,000 different patterns. Out of these, each pattern will have more blue, gold, or grey, and it's up to the person which looks best. Counting solely out of value, pattern #661 is the most sought after, and there only exists 114 of them on CSGOFloat. Out of these, there is not a single StatTrak™ Factory New version of it.
At this point, these skins are just rare because of the limited supply of cases, the low chance of hitting a StatTrak™ version, the low chance of getting a Factory New version, the low chance of hitting a pink, and the 1/1,000 chance of getting the correct pattern. There is actually 4 of these unboxed already if you could settle for a Minimal Wear one that is
Moving on, we can take a look at some of the rarer knives that aren't unboxed yet. A lot of these rare knives are StatTrak™ Factory New Ultraviolet ones, but some of these are actually unboxed. For instance, the StatTrak™ Bayonet | Ultraviolet (Factory New) has been around for a while.
One of the ones from that collection that hasn't yet been unboxed is the StatTrak™ Ursus Knife | Ultraviolet (Factory New). Here is a screenshot of how the normal Ursus Knife | Ultraviolet (Factory New) looks like:
But even now, this knife has a very possible chance of getting unboxed. What makes this one in particular rare is that you would need to combine StatTrak™, a very specific float that must be found in a very small range, and the knife itself. These look way cleaner than their more damaged counterparts, so there is definitely a reason why they're sought after.
We have now looked at rare skins, but we haven't paid any attention to the unobtainable skins. These may not seem rare, but they can be very rare. To this list, there are a bunch of skins you can think of:
* The AK47 | Redline (Factory New) - this is because of these being capped at the Minimal Wear float range.
* Certain souvenir skins - this is because varying rarities combined with a lot of combinations of stickers make it statistically impossible to get every single one. Only a time machine would help in this sense, where you could, in that case, obtain more souvenir packages for the future userbase.
* A bunch of unique sticker combinations and nametags on weapons. Making your skins stand out with decoration can make it near-impossible for someone else to get the exact same skin, pattern, and nametag unless they dedicate a lot of money and luck towards that goal.
While the end is a bit disappointing compared to the rest, there's no way not to generalize on skins like these. Not all skins can be considered unobtainable, especially if there is a slim chance of them ever existing. Furthermore, rarity does not equal value - and sentimental value can mean more than weird patterns or float values sometimes. Maybe you gave your friend an AK47 skin a few years ago that they haven't sold or traded away. That skin is probably worth more than the simple price tag that is attached to it, simply because of the fact that you gave them it.