Nepal is probably the rarest Then the limited time event shaders like the SRL or Crimson Doubles ones Or Infinite Link for the Refer a Friend Possibly the old Cryptarch ones like Arctic Proxy, God of War, etc.. It's hard(ish) to get ALL of the faction shaders but I feel like we're moving into pretty 'common' territory now... I've got most of the rare ones including all of the limited time event ones and Infinite Link, I'm just missing a few faction ones and I never got the Nepal one :( kinda regret that now but oh well, lesson learned... [spoiler]maybe Chatterwhite, Glowhoo, Queen's Web, etc.? These would only be rare if you were a Y2 who never played the old content though... Easily obtainable, but still maybe rare for those who didn't participate.[/spoiler]