Now that clever people have worked out how to extract the game's files I was looking at the list of item descriptions.

I thought I had found all the "Very Rare" items but it seems I missed two.

The list of very rare items:
Pinkies - Very rare box of treats known for their indefinite shelf life and astronomic sugar content.
Quayola Quayons - Very rare collection of Quayola's Brown Spectrum Quayons in excellent condition.
Wolf Goblet - Very rare antique jewel encrusted goblet. Looks to be of German craftsmanship.
Vault Boy Bobblehead - Very rare promotional Vault-Tec item.
Doom Marine Bobblehead - Very rare promotional id Tech item.
Shambler Plush - Very rare stuffed yeti-like demon. Watch out, it shoots lightning!
Blake Bobble Head - He's in RAGE!
Stuffed Mutant Dog - Collectors have strange tastes.

The are several Pinkies hidden throughout the game. I only found two, anyone manage to find more?
Wolf Goblet is from the secret Wolfenstein room in the Ghost Hideout.
Vault Boy Bobblehead is from Mayor Clayton's desk in Wellspring.
Doom Marine Bobblehead is from the secret Doom room in the Gearhead Vault.
Shambler Plush is from the secret Quake room in the Wasted Garage.
Blake Bobble Head is from Redstone's desk in Subway Town.

I don't know where the Quayola Quayons or Stuffed Mutant Dog are.

Also does anyone know what the Water Purifier items do? There were quite a few of them hidden around the place.

I see a reference in the file to Purified Water, can you some how make it and sell it? I remember an NPC saying water was valuable in Wellspring.

I found the crayons on one of my playthroughs. I think they are in the Dead City, but I can't remember. They're on a staircase you can walk up that does not lead anywhere (blocked off). I'm sure you could find it on YouTube.

I thought the water purifier was a easter egg referring to FallOut 3

Crayons are also in the Ghost hideout. You have to go back to the hide out for them after you finsh a mission.