This shotgun here in CFPH is ONLY obtainable through the Daily Beginner reward for 7 days. There are no other means of obtaining it since its not available in the Item Shop, Mega Lotto (Black Market) Achievements, Events etc.
It could be obtained via reward box (daily/weekly rewards or online attendance). Since the new online attendance system took place, there's no way to get it (even for 3 days). Months ago, there were some "Spend Vcoin, Get Free Items" events that allow players who spend money in-game to choose any weapons (in list of course, Noble Gold not included). There's M16A4, but instead of being permanent, it only has 365 days.
This weapon was never announced or released publically in the game, but it was only available for 5 players to get the weapon through a special halloween event. 3 of them got the weapon, while I got the 2011 capsules that was never released. I was super duper lucky to win the weapon.
In CFNA, there was a list of the rarest weapons in the game released at the end of 2016 however, it never got updated. But one of the weapons which is still rare from that list is; AK-47-S-Gilded Skull. Only one person owns this weapon permanently.
Another weapon which could be considered rare is the M4A1-S Transformers Noble Gold. Only 10 players own this weapon in CFNA.
In cf na there are weapons exclusive for owners of complete weapons Sets. Most outsanting is the m4a1 Red Dragon having just 3 owners and the the m4a1 Stripes obtained by only 2 people. Also weapons like mp5 camo and rpk camo are meanwhile very rare since they were availaible very early for limited time only and players owning these weapons either quit the game over the years or just don t play them anymore because they become quite weak compared the the new released weapons. When talking about temporary weapons that are currently available I agree with Game Fever, I never saw Chaos Hook once I think it wouldn t be exagerated to say that actually not a single player owns this weapon on na Servers since nobody warnt to play the required zm map anymore.
An AK47-WEM, I've only ever seen two players carry it during the lifetime I played in my server so it's arguably rarer than our national finals team sponsored CFS AK47 ...
They did offer during the 2010 WEM but I don't think it was permanent and the only way the two of them obtained it permanently was by participating in CFS NF where GMs offered any weapon of their choice ...