I'm not sure if these are rare enough to qualify being added to the addon, or if there's any other collectibles I missed... but those might be worth taking a look at:

• https://www.wowhead.com/item=166518/g-m-o-d#dropped-by
• https://www.wowhead.com/npc=147585/spawn-of-kragwa#comments
• https://www.wowhead.com/npc=147587/thunder-lizard-runt#comments
• https://www.wowhead.com/npc=147586/child-of-paku#comments

• Research: Can the items be bonus rolled? (Needs more data)
• Task: Add collectibles to the DB
• Task: Add waypoints for all BDA items (Just the raid itself, for now - see #59)
• Testing: Defeat detection for all bosses (bleh)

Added in c508763.